GM Service Manual Online
For 1990-2009 cars only

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at speeds above 40 km/h (25 mph). Steep grades may cause variations in the selected vehicle speeds.

The following are the main components of the cruise control system:

    • The accelerator pedal
    • The brake pedal position sensor
    • The Body Control Module (BCM)
    • The Driver Information Center (DIC)
    • The Instrument Panel Cluster (IPC)
    • The ON/OFF switch
    • The Engine Control Module (ECM) or Powertrain Control Module (PCM)
    • The RES/+ switch
    • The SET/- switch
    • The Throttle Actuator Control (TAC) module
    • The TAC motor
    • The vehicle speed sensor

Cruise Control Engaged

The cruise control system will engage and adjust vehicle speeds, based on the activation of the following cruise control switches:

    • The ON/OFF switch
    • The RES/+ switch
    • The SET/- switch

The ECM/PCM monitors the signal circuit of the cruise control switches. The ECM/PCM uses the cruise control set/coast and resume/accelerate switch signal circuit in order to determine when to capture and maintain the selected vehicle speed. The PCM uses the TAC module and the TAC motor in order to maintain the vehicle speed. For further review of the TAC system, refer to Throttle Actuator Control (TAC) System Description .

Ignition voltage is supplied to the cruise control switch from the 2A CRUISE SW fuse located in the I/P fuse block. The cruise control function switches are arranged in a resistive ladder design, with each cruise control function switch having a different resistance value. The ECM/PCM detects a specific voltage value that is associated with the cruise control function switch being activated. When the normally open cruise control ON/OFF switch is turned ON, the switch closes and the ECM/PCM detects a predetermined voltage signal on the cruise control switch signal circuit indicating that the ON/OFF switch is active. When the RES/+ switch or the SET/- switch are activated, the ECM/PCM detects the predetermined voltage signal on the switch signal circuit. To engage the cruise control system, turn the cruise control system ON by pressing the cruise ON/OFF button and momentarily activating the SET/- switch. The ECM/PCM will engage the cruise control system and the TAC module will record the vehicle speed. The ECM/PCM sends a class 2 message to the DIC in order to activate the CRUISE SET message. The ECM/PCM also sends a class 2 message to the IPC in order to illuminate the Cruise indicator. Pressing the accelerator pedal, while the cruise control system is engaged, will allow the driver to override the cruise control system in order to accelerate the vehicle beyond the current set vehicle speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override the current set vehicle speed via the SET/- switch or the RES/+ switch. When the cruise control system is engaged, activating and holding the SET/- switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the SET/- switch is released, the vehicle will maintain the current vehicle speed as the new set vehicle speed. Momentarily activating the SET/- switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the SET/- switch is activated, with the minimum vehicle speed being 37 km/h (23 mph). Activating and holding the RES/+ switch, when the cruise control system is engaged, will allow the vehicle to accelerate to a greater vehicle speed than the current set vehicle speed. When the RES/+ switch is released, the vehicle will maintain the current vehicle speed. Momentarily activating the RES/+ switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the RES/+ switch is pressed, with a maximum acceleration of 16 km/h (10 mph) over the current set vehicle speed . If the cruise control system is disengaged by pressing the brake pedal, momentarily activating the RES/+ switch will recall the previous vehicle speed

Cruise Control Disengaged

The ECM/PCM disengages the cruise control operation based on the signals from one of the following:

    • The brake pedal position (BPP) sensor
    • The ON/OFF switch

The BPP sensor is mounted on the brake pedal bracket. Pressing the brake pedal while the cruise control is engaged will disengage the cruise control system. The BCM monitors the brake pedal position sensor via the brake pedal position sensor signal circuit. The ECM/PCM detects a high voltage signal on stop lamp switch signal circuit from the BCM indicating that the brake pedal has been pressed. For further information on the brake pedal position sensor, refer to Exterior Lighting Systems Description and Operation .

When the cruise control ON/OFF switch is turned OFF, the switch closes and the ECM/PCM detects zero voltage on the cruise control cruise control switch signal circuit indicating that the ON/OFF switch is OFF.

When cruise control system has been disengaged, the ECM/PCM sends a class 2 message to the driver information center (DIC) in order to deactivate the CRUISE SET message. The ECM/PCM also sends a class 2 message to the instrument panel cluster (IPC) in order to turn off the Cruise indicator.

The vehicle speed stored in the memory of the TAC module will be erased when the OFF button is activated, or the ignition switch is turned OFF.

The cruise control system will disengage when the ECM/PCM detects that a driver override function has been active for approximately 60 seconds.

Cruise Control Inhibited

The ECM/PCM inhibits the cruise control operation when any of the following conditions exist:

    • A cruise control system DTC has been set.
    • The vehicle speed is less than 40.2 km/h (25 mph).
    • The vehicle speed is too high.
    • The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
    • The engine RPM is too low.
    • The engine RPM is too high.
    • The system voltage is not between 9 volts and 16 volts.
    • The antilock brake system/traction control system is active for more than 2 seconds.