GM Service Manual Online
For 1990-2009 cars only

Cruise Control Description and Operation W/ETC

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. However, steep grades may cause variations in the selected speeds. The electronic cruise control system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE, and TAP-UP or TAP-DOWN.

The main parts of the cruise control system are:

    • The Throttle Actuator Control (TAC) Module
    • The function control switches
    • The stop lamp switch assembly
    • The TCC Brake (cruise release) switch assembly
    • The clutch pedal position sensor (CPP), if equipped

The cruise control system uses the TAC module to maintain the desired vehicle cruise speed and operation. The TAC and the powertrain control module (PCM) communicate together to vary the throttle opening in each different cruise control mode. The PCM monitors vehicle speed and operates the throttle actuator. The throttle actuator operates in response to the TAC module, to maintain the desired cruise speed. The throttle actuator motor moves the throttle blade. The PCM assembly contains a low speed limit which will prevent system engagement below a minimum speed of 40 km/h (25 mph). The TAC or PCM module assemblies are not serviceable.

The operation of the TAC module is through the function control switches located on the multifunction turn signal lever. The cruise control function control switches includes the ON/OFF, SET/COAST, R/A (resume/accelerate). The switch assembly provides driver control of the cruise control system.

The stop lamp switch, TCC Brake switch (cruise release) or CPP switch if equipped, is used to disengage the cruise control. A cruise control release switch circuit and a stoplamp switch circuit are used. The stop lamp, TCC Brake and CPP switches are mounted to the brake pedal bracket . To disengage the system the driver presses the brake pedal or clutch pedal, if equipped. The speed of the vehicle at brake actuation will be stored in the memory of the TAC module.

With cruise control, the vehicle can maintain a speed of about 40 km/h (25 mph) or more without keeping your foot on the accelerator. When the driver turns off the cruise control ON/OFF switch or ignition switch, the cruise control turns off. The vehicle speed stored in the memory of the TAC module will be lost.

Ignition positive voltage is supplied from the electronic throttle control (ETC) fuse, to the TAC module. The TAC module is grounded to G110. When the cruise control ON/OFF switch is on, ignition positive voltage is applied to the cruise on switch signal terminal of the TAC module. If the driver has not pressed the brake pedal or clutch pedal if equipped, ignition positive voltage is supplied through the switches, to the cruise control release switch signal and clutch signal, if equipped, terminals of the PCM. Cruise control is canceled when the driver presses either the brake pedal or clutch pedal, if equipped. The stop lamp switch closes, applying battery positive voltage to the stop lamp signal circuit of the TAC module. Voltage is also removed from the cruise release signal circuit and the clutch switch signal circuit, if equipped, at the PCM. When pressing the SET/COAST button on the multifunction turn signal lever, ignition positive voltage is applied to the set/coast switch signal terminal of the TAC module. When pressing the R/A (resume/accelerate) on the control switch, ignition positive voltage is applied to the resume/accelerate switch signal terminal of the TAC module.

When the cruise switch is in the ON position, and the driver presses the SET/COAST button, the TAC module notifies the PCM that the cruise control is requested. The PCM then checks to see that the cruise control enable criteria is met. If the cruise control criteria has been met the PCM sends a class 2 message to the instrument panel cluster (IPC) to illuminate the cruise light, if equipped

The PCM will inhibit cruise control:

    • When vehicle speed is less than 40 km/h (25 mph).
    • When in PARK, REVERSE, NEUTRAL, or 1st gear.
    • With low engine RPM
    • With high engine RPM (fuel cut-off)
    • When vehicle speed is too high
    • When an over or under charged battery voltage condition exists
    • Antilock brake system/traction control system is active for more than 2 seconds

If the PCM determines that any of the cruise control inhibit conditions are present, the PCM will disengage the cruise control. The PCM accomplishes this through data communication with the TAC module. If the PCM disables the cruise control for an inhibiting event it will record the reason for disengagement in the Disengage Definition data file.

Cruise Control Description and Operation WO/ETC

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. However, steep grades may cause variations in the selected speeds. The electronic cruise control system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE, and TAP-UP or TAP-DOWN.

The main parts of the cruise control system are:

    • The cruise control module assembly
    • The function control switches
    • The cruise control release switch
    • The stop lamp switch assembly
    • The vehicle speed sensor

The cruise control system uses the cruise control module assembly to maintain the desired vehicle cruise speed and operation. The cruise control module assembly has a controller and an electric stepper motor to vary the throttle in each different cruise control mode. The controller monitors vehicle speed and operates the stepper motor. The stepper motor operates in response to the controller, to maintain the desired cruise speed. The electric stepper motor moves a strap that is attached to the cruise control cable which moves the throttle linkage. The cruise control module assembly contains a low speed limit which will prevent system engagement below a minimum speed of 40 km/h (25 mph). The module assembly is not serviceable.

The operation of the controller is controlled by the function control switches located on the steering wheel. The cruise control functional control switches include the ON/OFF, SET/COAST, R/A (resume/accelerate). The switches provide driver control of the cruise control system.

The cruise control release switch and stoplamp switch are used to disengage the cruise control. A release switch assembly and a stoplamp switch assembly are mounted on the brake pedal bracket . To disengage the system the driver presses the brake pedal. The speed of the vehicle at brake actuation will be stored in the memory of the cruise module.

With cruise control, you can maintain a speed of about 40 km/h (25 mph) or more without keeping your foot on the accelerator. When the driver turns off the on/off switch or ignition switch, the cruise control turns off. The vehicle speed stored in the memory of the cruise module will be lost.

Ignition 1 voltage is supplied from the cruise control fuse, to the cruise control module. The cruise control module is grounded to the chassis. When the cruise control ON/OFF switch is on, ignition 1 voltage is applied to the cruise control on switch signal circuit of the cruise control module. If the driver has not pressed the brake pedal, ignition 1 voltage is supplied through the TCC/Brake (cruise release) switch, to the cruise release signal circuit of the cruise control module. When the driver presses the brake pedal, battery positive voltage is supplied from the stop lamp fuse, through the closed stop lamp switch to the stop lamp switch signal circuit of the cruise control module. When the SET/COAST button is pressed , ignition positive voltage is applied to the cruise control set/coast switch signal circuit of the cruise control module. When pressing the R/A (resume/accelerate), ignition positive voltage is applied to the cruise control resume/ accelerate switch signal circuit of the cruise control module.

The cruise control module receives a vehicle speed signal input from the Powertrain Control Module (PCM). In operation, the voltage varies between 0 V and 5 V.

The cruise control module, cruise engaged circuit, sends a signal to the PCM when cruise is engaged. The cruise control module, cruise inhibit signal circuit, is a circuit used by the PCM to disengage cruise control when conditions inconsistent with cruise operation are present.

After the cruise control engaged criteria has been met and the cruise ON and Set/Coast have been commanded, the cruise control module sends a signal to the PCM that the cruise control is engaged.

The PCM will inhibit cruise control:

    • When vehicle speed is less than 40 km/h (25 mph).
    • When PARK, REVERSE, NEUTRAL, or 1st gear is indicated.
    • With low engine RPM
    • With high engine RPM (fuel cut-off)
    • When vehicle speed is to high
    • When an over or under charged battery voltage condition exists
    • Antilock brake system/traction control system is active for more than 2 seconds

If the PCM determines that any of the cruise control inhibit conditions are present, the PCM will disengage the cruise control . The PCM accomplishes this by opening the cruise control inhibit signal circuit.