Cruise Control Description and Operation 3.5L

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 powertrain control module (PCM) monitors the signal circuit of the cruise control switches. The 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 monitors the vehicle speed sensor circuit in order to determine the vehicle speed. The PCM uses the throttle actuator control (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 in Engine Controls - 3.5L (LX9).

Ignition voltage is supplied to the cruise control switch from the 2-amp CRUISE/SWITCH fuse located in the instrument panel (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 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 PCM detects a predetermined voltage signal on the cruise control cruise control set/coast and resume/accel switch signal circuit indicating that the ON/OFF switch is active. When the RES/+ switch or the SET/- switch are activated, the PCM detects the predetermined voltage signal on the cruise control set/coast and resume/accel 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 PCM will engage the cruise control system and the TAC module will record the vehicle speed. The PCM sends a class 2 message to the instrument panel cluster (IPC) in order to illuminate the Cruise indicator. The SET/- switch or the RES/+ switch will remain inactive when the PCM has not received the predetermined voltage signal from the ON/OFF switch. 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 and 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. When the cruise control system is engaged, 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. When the cruise control system is engaged, 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 . Momentarily activating the RES/+ switch will recall the previous vehicle speed, after the cruise control system is disengaged by pressing the brake pedal or by activating the CANCEL switch.

The powertrain control module (PCM) disengages the cruise control operation based on the signals from one of the following:

The body control module (BCM) monitors the signal circuit of the CANCEL switch. When the CANCEL switch is activated, the BCM detects a high signal voltage on the cruise control cancel switch signal circuit. The BCM sends a class 2 message to the PCM in order to disengage the cruise control system.

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 BPP sensor via the BPP sensor signal circuit. The 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 BPP sensor, refer to Exterior Lighting Systems Description and Operation or Brake Pedal Position Sensor Calibration in Lighting Systems.

When the cruise control ON/OFF switch is turned OFF, the switch closes and the PCM detects zero voltage on the cruise control cruise control set/coast and resume/accel switch signal circuit indicating that the ON/OFF switch is OFF. When the ON/OFF switch is turned OFF, the PCM 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 throttle actuator control (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 PCM detects that a driver override function has been active for approximately 60 seconds.

The powertrain control module (PCM) inhibits the cruise control operation when any of the following conditions exist: