Cruise Control Description and Operation L81

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

The ECM monitors the signal circuits of the cruise control switches in order to determine when to capture and maintain the selected vehicle speed. The ECM uses the TAC motor in order control and maintain the vehicle speed. For further information on the TAC system, refer to Throttle Actuator Control (TAC) System Description in Engine Controls - 3.0L (L81)

Ignition positive voltage is supplied from the 2-ampere CRUISE SWITCH fuse to the cruise control switch via the ignition 3 voltage circuit. When the normally open cruise control On/Off switch is turned On, the switch closes and the amber switch indicator illuminates, and the ECM detects a high signal voltage on the cruise control on switch signal circuit. When the normally open set/coast switch is pressed, the switch closes and the ECM detects a high signal voltage on the cruise control set/coast switch signal circuit. To engage the cruise control system, turn the On/Off switch On and momentarily press the set/coast switch. The ECM will confirm that the cruise control enable criteria has been achieved. The ECM will engage the cruise control system and record the selected vehicle speed. The ECM sends a class 2 message to the instrument panel cluster in order to illuminate the cruise control 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/coast switch and the resume/accel switch. When the cruise control system is engaged, pressing and holding the set/coast switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the set/coast switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily pressing the set/coast switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the set/coast is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). When the normally open resume/accel switch is activated, the switch closes and the ECM detects a high signal voltage on the cruise control resume/accel switch signal circuit. Pressing and holding the resume/accel 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 resume/accel switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily pressing the resume/accel switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the resume/accel switch is pressed, with the maximum acceleration total of 16 km/h (10 mph) over the current set vehicle speed. Momentarily pressing and releasing the resume/accel switch, after the cruise control system has been disengaged by pressing the brake pedal, will recall the previous set vehicle speed that is recorded in the ECM.

The ECM disengages the cruise control operation based on the signals from the following switches:

The cruise brake switch and the stop lamp switch are mounted on the brake pedal bracket. When the brake pedal is applied, the normally closed cruise brake switch opens and the normally open stop lamp switch closes. The ECM detects a low signal voltage on the cruise control release signal circuit and a high signal voltage on the stop lamp switch signal circuit. The vehicle speed stored in the memory of the ECM will be erased when the cruise control On/Off button is turned OFF, or the ignition switch is turned OFF.

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

When the cruise control system is disengaged, the ECM sends a class 2 message to the instrument panel cluster (IPC) in order to deactivate the cruise indicator.

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

Cruise Control Description and Operation L61

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 system uses the cruise control module assembly to maintain the desired vehicle cruise speed and operation. The cruise control module assembly has an electronic controller and an electric stepper motor to vary the throttle in each different cruise control mode. The electric controller monitors vehicle speed and operates the electric stepper motor. The stepper motor operates in response to the electronic 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 electronic 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 and R/A (resume/accelerate) switch. The switch assembly provides driver control of the cruise control system.

The TCC/Brake switch and stop lamp switch control the cruise control release signal and stop lamp signal. These signal circuits are used to disengage the cruise control. The switch assemblies are mounted on the brake pedal bracket. To disengage the system electrically 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 the ignition switch, the cruise control turns OFF. The vehicle speed stored in the memory of the cruise module will be lost.

Ignition positive voltage is supplied from the cruise fuse, to the cruise control module. The cruise control switch is supplied ignition positive voltage by the cruise switch fuse. The cruise control module is grounded to the chassis. When the cruise control on/off switch is on, ignition positive voltage is applied to the cruise on switch signal circuit of the cruise control module. If the driver has not pressed the brake pedal, ignition positive voltage is supplied through the cruise control release circuit, to the cruise control release signal terminal of the cruise control module. On vehicles equipped with a manual transmission, a clutch switch is wired in series on this circuit and operates the same. 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 terminal of the cruise control module. As this operation occurs, ignition positive voltage is removed from the cruise release signal circuit. If equipped, voltage is also removed from the cruise release signal circuit when the clutch pedal is pressed. When the set/coast is pressed on the control switch, ignition positive voltage is applied to the set/coast switch signal terminal of the cruise control 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 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 0-5 volts.

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

After the cruise control engage criteria has been met and the cruise control 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:

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.