GM Full-Size Trucks 1988-1998 Repair Information

General Information

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1988-95 Models

The electro-motor cruise control system maintains a desired speed under normal driving conditions. The main components of the system are the multi-function lever, cruise control module, vehicle speed sensor, vehicle speed sensor calibrator module, release switches and electrical harness.

The module contains a stepper motor and a electronic controller. The controller monitors the vehicle speed and operates the stepper motor. The motor operates a band and throttle cable to maintain the desired speed. The module also contains a low speed limit that will prevent system operation below 25 mph (40 km/h). The controller is activated by the signals from the multi-function lever located on the turn signal lever. A release switch which is either mounted on the brake or clutch pedal (if equipped with a manual transmission), disengages the system when the brake or clutch pedal is depressed and the throttle then returns to idle.

1996-98 Models

Gasoline Engines

The cruise control system used on vehicles equipped with gasoline engines comprises of the Vehicle Control Module (VCM), cruise control module, the multi-function lever and the brake release switch. The cruise control module contains a stepper motor which is used to vary throttle position. The cruise control module receives its commands from the multi-function lever and the vehicle speed from the VCM. Based on these commands the cruise control module will control vehicle speed.

Diesel Engines

The cruise control system used on vehicles equipped with diesel engines comprises of the Powertrain Control Module (PCM), electronic throttle system, the Vehicle Speed Sensor Buffer (VSSB), the multi-function lever and the brake release switch. The PCM receives commands from the multi-function lever and the vehicle speed information from the VSSB. Based on the commands from the multi-function switch and the VSSB, the PCM the uses the electronic throttle system to control vehicle speed.

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Cruise control troubleshooting

 
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