Cruise Control System - Trucks Diesel GMC Savana I

MODEL IDENTIFICATION

MODEL IDENTIFICATION

DESCRIPTION & OPERATION

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. Steep grades may cause variations in selected speeds. System has capability to cruise, coast, resume speed, accelerate, and tap-up and tap-down.

The main components of the cruise control system include the Powertrain Control Module (PCM), functional control switches, Vehicle Speed Sensor (VSS), Vehicle Speed Sensor Buffer (VSSB), and brake and clutch release switches. See COMPONENT LOCATIONS .

CRUISE CONTROL FUNCTIONAL SWITCHES

Note. Multifunction lever may also be referred to as combination switch.

Functional control switches are located on the end of the multifunction lever, which also serves as a turn signal lever. Functional control switches include a SET button and a sliding main switch with OFF, ON and R/A positions.

OFF

System disengages when switch is turned off.

System is ready to be set when switch is turned on.

SET (Set/Coast)

Spring-loaded SET button engages cruise. During engagement, if SET button is pressed and held, vehicle decelerates (cruise disengages) until button is released. When button is released, cruise engages and maintains new set speed. Also, by quickly pressing and releasing (tapping) this button, the set speed is "tapped-down" in one MPH increments.

R/A (Resume/Accelerate)

Spring-loaded R/A switch will not initially set cruise speed, but when cruise has been disengaged by braking, momentarily sliding this switch to R/A position will cause cruise to resume previously set speed. This is the resume function. Accelerate function occurs when R/A switch is held in position for more than one second. This causes the vehicle to accelerate until switch is released. When released, system maintains new set speed. Also, by quickly pressing and releasing (tapping) this switch, the set speed is "tapped-up" in one MPH increments.

POWERTRAIN CONTROL MODULE (PCM)

When cruise control switch is on and SET button is pressed, vehicle speed input from vehicle speed sensor buffer will be stored in Powertrain Control Module (PCM). PCM will send signals to the electronic throttle control system to control and maintain vehicle speed. Electronic throttle is a servo system which supplies information to PCM. PCM will increase or decrease throttle position based on engine load to maintain vehicle speed.

BRAKE & CLUTCH RELEASE SWITCHES

Brake and clutch release switches allow current flow to PCM when brakes and clutch are released. When brake or clutch pedal is depressed, voltage supply to cruise control circuit in PCM is interrupted. Brake switch may incorporate brakelight and torque converter clutch switch.

Vehicle Speed Sensor (VSS) Buffer

Vehicle Speed Sensor (VSS) buffer receives a signal from VSS permanent magnet generator, indicating vehicle speed. This signal is then processed by VSS buffer and supplied to Powertrain Control Module (PCM) and speedometer.

Vehicle Speed Sensor (VSS)

VSS is mounted in transmission. VSS produces an AC signal with a frequency proportional to speed at which transmission assembly output shaft rotates, which is also proportional to vehicle speed. AC signal produced by VSS is amplified and converted to a rate of 4000 pulses per mile by VSSB. The 4000 pulse signal is sent to Powertrain Control Module (PCM) and speedometer. These components then convert number of pulses per mile to pulses per second to determine speed of vehicle.

COMPONENT LOCATIONS

COMPONENT LOCATIONS

TCC/BRAKE SWITCH (MOTORHOME)

Note. On all models except Motorhome, the brake switch is not adjustable.

To adjust, depress pedal and push switch until switch body is fully seated on retainer. Pull pedal toward rear of vehicle, against pedal stop (until clicking sound cannot be heard while pulling pedal). Switch will adjust to proper position in retainer. Electrical contact should occur when brake pedal is applied for a distance of .45-.95" (11-24 mm).

PRELIMINARY INSPECTION

1. Check fuses, and replace as necessary. Visually inspect for broken or open wires. Check for a broken or partially broken wire inside insulation which could cause system malfunction but prove good in a continuity/voltage check with system disconnected.
2. Check for Diagnostic Trouble Codes (DTCs). If any codes are present, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
3. Ensure brake switch is installed correctly. On Motorhome, see «TCC/BRAKE SWITCH (MOTORHOME)»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel__tccbrake-switch-motorhome) under ADJUSTMENTS. On all models, ensure center high mounted brakelight is operating.
4. Ensure any aftermarket electronic equipment is properly installed. Repair as necessary. If no problems are found, go to «SYSTEM CHECK»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel__system-check) .

SYSTEM CHECK

1. Drive vehicle at a speed greater than 25 MPH. Move cruise control main switch to ON position. Press SET button once and release. Remove foot from accelerator pedal. Vehicle should maintain set speed.
2. Hold slider switch in R/A position until vehicle speed increases 4-5 MPH. Vehicle should accelerate and maintain new set speed. Press SET button until vehicle speed decreases 4-5 MPH. Vehicle should decelerate and maintain new set speed.
3. Depress brake pedal slightly. Cruise control system should disengage. Press slider switch to R/A position once and release. Vehicle should accelerate and maintain previously set speed. Tap-up R/A switch (less than 3/4 of a second). Vehicle speed should increase one MPH. Tap-down SET button (less than 3/8 of a second). Vehicle speed should decrease one MPH.
4. Simultaneously press SET button and R/A switch. Cruise control system should disengage, but retain previously set speed in memory. Move main switch to OFF position. Cruise control system should disengage, and set speed should be erased from memory. If cruise control system does not function as specified, perform appropriate test under «SYSTEM TESTS»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) .

CRUISE CONTROL IS INOPERATIVE

Note. To avoid misdiagnosis, perform PRELIMINARY INSPECTION under TROUBLE SHOOTING . Check for stored DTCs. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

"C" & "K" Series Pickups, Sierra, Suburban, Tahoe & Yukon

1. Disconnect Powertrain Control Module (PCM) 24-pin connector C2 (Brown). Turn ignition switch to RUN position. Connect a test light between PCM connector C2 (harness side) terminal A11 (Gray wire) and ground. Turn cruise control switch to ON position. If test light does not illuminate, go to next step. If test light illuminates, go to step 4 .
2. Disconnect multifunction lever (cruise control switch) connector, located at base of steering column. Connect a test light between multifunction lever (cruise control switch) connector (harness side) terminal A13 (Brown wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, repair open in Brown wire between instrument panel fuse block and multifunction lever (cruise control switch).
3. Ensure cruise control switch is still in the ON position. Turn ignition switch to OFF position. Connect an ohmmeter between multifunction lever (cruise control switch) connector (pigtail side) terminals A13 (Brown wire) and A12 (Gray wire). If continuity exists, repair open in Gray wire between multifunction lever (cruise control switch) and PCM. If continuity does not exist, repair open in Brown wire or Gray wire of multifunction lever (cruise control switch) pigtail. If Brown wire and Gray wire are okay, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article.
4. Connect a test light between PCM connector C2 (harness side) terminal B11 (Dark Blue wire) and ground. Press and hold cruise control switch in SET position. If test light does not illuminate, go to next step. If test light illuminates, go to step 6 .
5. Disconnect multifunction lever (cruise control switch) connector. Connect an ohmmeter between multifunction lever (cruise control switch) connector (pigtail side) terminals A13 (Brown wire) and A14 (Dark Blue wire). If continuity exists, repair open in Dark Blue wire between multifunction lever (cruise control switch) and PCM. If continuity does not exist, repair open in Dark Blue wire of multifunction lever (cruise control switch) pigtail. If Dark Blue wire is okay, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article.
6. Connect a test light between PCM connector C2 (harness side) terminal B10 (White wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
7. Disconnect brake switch connector. Connect an ohmmeter between brake switch terminals "B" (Orange wire) and "A" (White wire). If continuity exists, replace brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If continuity does not exist, repair short to voltage in White wire between brake switch and PCM.
8. Apply brake pedal. If continuity does not exist, go to next step. If continuity exists, go to step 11 .
9. Disconnect brake switch connector. Connect a test light between brake switch connector (harness side) terminal "B" (Orange wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, repair open in Orange wire between instrument panel fuse block and brake switch.
10. Connect an ohmmeter between brake switch terminals "B" (Orange wire) and "A" (White wire). Apply brake pedal. If continuity does not exist, replace brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If continuity exists, repair open in White wire between brake switch and PCM.
11. Connect a test light between PCM connector C2 (harness side) terminal B9 (Purple wire on A/T or Brown/White wire on M/T) and ground. If test light does not illuminate, go to next step. If test light illuminates, replace PCM.
12. Disconnect brake switch connector. Connect a test light between brake switch connector (harness side) terminal "F" (Brown wire) and ground. If test light illuminates, go to next step (A/T) or step 14 (M/T). If test light does not illuminate, repair open in Brown wire between instrument panel fuse block and brake switch.
13. Connect an ohmmeter between brake switch terminals "F" (Brown wire) and "E" (Purple wire). Apply brake pedal. If continuity exists, replace brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If continuity does not exist, repair open in Purple wire between brake switch and PCM.
14. Connect a test light between clutch switch connector (harness side) terminal "B" (Purple wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, repair open in Purple wire between clutch switch and brake switch.
15. Connect a test light between clutch switch connector (harness side) terminal "D" (Brown/White wire) and ground. If test light does not illuminate, replace clutch switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If test light illuminates, repair open in Brown/White wire between clutch switch and PCM.

Express & Savana

1. Disconnect Powertrain Control Module (PCM) 24-pin connector C2 (Brown). Turn ignition switch to RUN position. Connect a test light between PCM connector C2 (harness side) terminal A11 (Gray wire) and ground. Turn cruise control switch to ON position. If test light does not illuminate, go to next step. If test light illuminates, go to step 4 .
2. Disconnect multifunction lever (cruise control switch) connector at base of steering column. Connect a test light between multifunction lever (cruise control switch) connector (harness side) terminal A13 (Brown wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, repair open in Brown wire between instrument panel fuse block and multifunction lever (cruise control switch).
3. Connect an ohmmeter between multifunction lever (cruise control switch) connector (pigtail side) terminals A13 (Brown wire) and A12 (Gray wire). If continuity exists, repair open in Gray wire between multifunction lever (cruise control switch) and PCM. If continuity does not exist, repair open in Brown wire or Gray wire of multifunction lever (cruise control switch) pigtail. If Brown wire and Gray wire are okay, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article.
4. Connect a test light between PCM connector C2 (harness side) terminal B11 (Dark Blue wire) and ground. Press and hold cruise control switch in SET position. If test light does not illuminate, go to next step. If test light illuminates, go to step 6 .
5. Disconnect multifunction lever (cruise control switch) connector. Connect an ohmmeter between multifunction lever (cruise control switch) connector (pigtail side) terminals A13 (Brown wire) and A14 (Dark Blue wire). If continuity exists, repair open in Dark Blue wire between multifunction lever (cruise control switch) and PCM. If continuity does not exist, repair open in Dark Blue wire of multifunction lever (cruise control switch) pigtail. If Dark Blue wire is okay, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article.
6. Connect a test light between PCM connector C2 (harness side) terminal B10 (White wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
7. Disconnect TCC/brake switch connector. Connect an ohmmeter between TCC/brake switch terminals "E" (Orange wire) and "F" (White wire). If continuity exists, replace TCC/brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If continuity does not exist, repair short to voltage in White wire between TCC/brake switch and PCM.
8. Apply brake pedal. If continuity does not exist, go to next step. If continuity exists, go to step 11 .
9. Disconnect TCC/brake switch connector. Connect a test light between TCC/brake switch connector (harness side) terminal "E" (Orange wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, repair open in Orange wire between instrument panel fuse block and TCC/brake switch.
10. Connect an ohmmeter between TCC/brake switch terminals "E" (Orange wire) and "F" (White wire). Apply brake pedal. If continuity does not exist, replace TCC/brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If continuity exists, repair open in White wire between TCC/brake switch and PCM.
11. Connect a test light between PCM connector C2 (harness side) terminal B9 (Purple wire) and ground. If test light does not illuminate, go to next step. If test light illuminates, replace PCM.
12. Disconnect TCC/brake switch connector. Connect a test light between TCC/brake switch connector (harness side) terminal "D" (Brown wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, repair open in Brown wire between instrument panel fuse block and TCC/brake switch.
13. Connect an ohmmeter between TCC/brake switch terminals "D" (Brown wire) and "C" (Purple wire). Apply brake pedal. If continuity exists, replace TCC/brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If continuity does not exist, repair open in Purple wire between TCC/brake switch and PCM.

Motorhome

1. Disconnect Powertrain Control Module (PCM) 24-pin connector C2 (Brown). Turn ignition switch to RUN position. Connect a test light between PCM connector C2 (harness side) terminal B9 (Purple wire) and ground. If test light illuminates, go to next step. If test light does not illuminate, check TCC/brake switch for proper adjustment. See «TCC/BRAKE SWITCH (MOTORHOME)»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel__tccbrake-switch-motorhome) under ADJUSTMENTS. If TCC/brake switch is properly adjusted, repair open in Purple wire between TCC/brake switch and PCM. If Purple wire is okay, replace TCC/brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION.
2. Connect a test light between PCM connector C2 (harness side) terminal B10 (Light Blue wire) and ground. If test light does not illuminate, go to next step. If test light illuminates, check brake switch for proper adjustment. See «TCC/BRAKE SWITCH (MOTORHOME)»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel__tccbrake-switch-motorhome) under ADJUSTMENTS. If brake switch is properly adjusted, repair short to voltage in Light Blue wire between brake switch and PCM.
3. Turn cruise control switch to ON position. Connect a test light between PCM connector C2 (harness side) terminal A11 (Gray wire) and ground. If test light does not illuminate, go to next step. If test light illuminates, go to step 6 .
4. Connect a test light between ground and multifunction lever (cruise control switch) connector (harness side) terminal "B" (Gray wire), located at base of steering column. If test light does not illuminate, go to next step. If test light illuminates, repair open in Gray wire between multifunction lever (cruise control switch) and PCM.
5. Connect a test light between multifunction lever (cruise control switch) connector (harness side) terminal "A" (Brown wire) and ground. If test light illuminates, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article. If test light does not illuminate, repair open in Brown wire between multifunction lever (cruise control switch) and instrument panel fuse block.
6. Connect a test light between PCM connector C2 (harness side) terminal B11 (Dark Blue wire) and ground Press and hold cruise control switch in SET position. If test light does not illuminate, go to next step. If test light illuminates, diagnose vehicle speed sensor buffer. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If vehicle speed sensor buffer is okay, replace PCM.
7. Connect a test light between multifunction lever (cruise control switch) connector (harness side) terminal "D" (Dark Blue wire) and ground. Press and hold cruise control switch in SET position. If test light does not illuminate, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article. If test light illuminates, repair open in Dark Blue wire between multifunction lever (cruise control switch) and PCM.

"C" & "K" Series Pickups, Express, Savana, Sierra, Suburban, Tahoe & Yukon

1. Disconnect multifunction lever (cruise control switch) connector, located at base of steering column. Connect an ohmmeter between multifunction lever (cruise control switch) connector (pigtail side) terminals A13 (Brown wire) and A15 (Gray/Black wire). While observing ohmmeter, press and hold cruise control switch in R/A position. If continuity exists, go to next step. If continuity does not exist, repair open in Gray/Black wire of multifunction lever (cruise control switch) pigtail. If Gray/Black wire is okay, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article.
2. Disconnect Powertrain Control Module (PCM) 32-pin connector C1 (Brown). Connect an ohmmeter between PCM connector C1 (harness side) terminal D10 (Gray/Black wire) and multifunction lever (cruise control switch) connector (harness side) terminal A15 (Gray/Black wire). If continuity exists, replace PCM. If continuity does not exist, repair open in Gray/Black wire between multifunction lever (cruise control switch) and PCM.

1. Disconnect Powertrain Control Module (PCM) 32-pin connector C1 (Brown). Turn ignition switch to RUN position. Connect a test light between PCM connector C1 (harness side) terminal D10 (Gray/Black wire) and ground. Press and hold cruise control switch in R/A position. If test light does not illuminate, go to next step. If test light illuminates, replace PCM.
2. Connect a test light between multifunction lever (cruise control switch) connector (harness side) terminal "C" (Gray/Black wire) and ground. Press and hold cruise control switch in R/A position. If test light illuminates, repair open in Gray/Black wire between multifunction lever (cruise control switch) and PCM. If test light does not illuminate, replace multifunction lever (cruise control switch). See appropriate STEERING COLUMN SWITCHES article.

1. Disconnect Powertrain Control Module (PCM) 24-pin connector C2 (Brown). Turn ignition switch to RUN position. Connect a test light between PCM connector C2 (harness side) terminal B9 (Purple wire on A/T or Brown/White wire on M/T) and ground. While observing test light, apply brake pedal. If test light remains illuminated, go to next step. If test light goes out, replace PCM.
2. Disconnect brake switch connector. Connect a test light between brake switch connector (harness side) terminal "E" (Purple wire) and ground. If test light does not illuminate, replace brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If test light illuminates, repair short to voltage in Purple wire between brake switch, PCM and Electronic Brake Control Module (EBCM).

1. Disconnect Powertrain Control Module (PCM) 24-pin connector C2 (Brown). Turn ignition switch to RUN position. Connect a test light between PCM connector C2 (harness side) terminal B9 (Purple wire) and ground. Test light should be illuminated. While observing test light, apply brake pedal. If test light remains illuminated, go to next step. If test light goes out, replace PCM.
2. Disconnect TCC/brake switch connector. Connect a test light between TCC/brake switch connector (harness side) terminal "C" (Purple wire) and ground. If test light does not illuminate, replace TCC/brake switch. See «BRAKE & CLUTCH RELEASE SWITCHES»(/gmc/savana/i-1996-2002/remont/cruise-control-systems/#cruise-control-system-trucks-diesel) under REMOVAL & INSTALLATION. If test light illuminates, repair short to voltage in Purple wire between TCC/brake switch, PCM and Electronic Brake Control Module (EBCM).

REMOVAL & INSTALLATION

Note. Multifunction lever may also be referred to as combination switch.

Functional control switches are located on the end of the multifunction lever, which also serves as a turn signal lever. Switches are not serviceable and must be replaced with multifunction lever as an assembly. See appropriate STEERING COLUMN SWITCHES article.

Removal & Installation (Except Motorhome)

1. Disconnect negative battery cable. Disable air bag system. See appropriate AIR BAG RESTRAINT SYSTEMS article. Using snap ring pliers, remove pushrod retainer from pedal pin. Remove switch from pushrod. Disconnect electrical connectors from switch.
2. To install, reverse removal procedure. When installing pushrod retainer onto pedal pin, use a 7/16" socket to push NEW clip onto pin.

Removal & Installation (Motorhome)

Disconnect negative battery cable. Disconnect electrical connectors from switch. Remove switch. To install, reverse removal procedure. Adjust switch. See TCC/BRAKE SWITCH (MOTORHOME) under ADJUSTMENTS.

Disconnect negative battery cable. Raise and support vehicle. Disconnect VSS electrical connector. Remove VSS mounting bolt. Remove VSS from transmission. Remove "O" ring from VSS. To install, reverse removal procedure. Lubricate "O" ring with transmission fluid. On A/T models, tighten bolt to 97 INCH lbs. (11 N.m). On M/T models, tighten bolt to 16 ft. lbs. (22 N.m).

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Cruise Control System Wiring Diagram ("C" & "K" Series Pickups, Suburban, Tahoe & Yukon - Diesel). Scheme 1

Cruise Control System Wiring Diagram (Express & Savana - Diesel). Scheme 2

Cruise Control System Wiring Diagram (Motorhome - Diesel). Scheme 3

See also:
• COMPONENT LOCATIONS
• TCC/BRAKE SWITCH (MOTORHOME)
• SYSTEM CHECK
• SYSTEM TESTS