Cruise Control: Description and Operation

CRUISE CONTROL DESCRIPTION AND OPERATION

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 (BPP) sensor
- The body control module (BCM)
- The on/off switch
- The engine control module (ECM)
- The RES + switch
- The SET - switch
- The throttle actuator control (TAC) motor
- The vehicle speed sensor (VSS)

Cruise Control Engaged
The Cruise Control System will engage and adjust vehicle speeds, based on the activation of the following cruise control switches:
- On/off
- RES +
- SET -

The engine control module (ECM) monitors the signal circuit of the cruise control switches. The ECM uses the cruise control set/coast and resume/accelerate switch signal circuit in order to determine when to capture and maintain the vehicle speed. The ECM monitors the vehicle speed signal circuit in order to determine the vehicle speed. The ECM uses the throttle actuator control (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 Computers and Control Systems - 3.6L.

Ignition voltage is supplied to the cruise control switch from the 2-amp CRUISE SW 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 ECM 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 amber cruise control on/off switch illuminates. The ECM also 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. Similarly, when the normally open RES + switch or the normally open SET - switch are activated, the ECM detects the predetermined voltage signal on the cruise control set/coast and resume/accel switch signal circuit. To engage the Cruise Control System, press the cruise on/off button On and momentarily activate the SET - switch. The ECM will engage the Cruise Control System and the ECM will record the vehicle speed. The ECM sends a class 2 message to the instrument panel cluster (IPC) in order to activate the Cruise indicator. The SET - switch or the RES + switch will remain inactive when the ECM 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 vehicle set 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. The minimum vehicle speed for the tap down function is 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 as the new vehicle set 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. The tap up function will only accelerate the vehicle a total 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.

Cruise Control Disengaged
The engine control module (ECM) 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 body control module (BCM) monitors the BPP sensor via the brake pedal position sensor signal circuit. The ECM 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, refer to Exterior Lighting Systems Description and Operation and to Brake Pedal Position Sensor Calibration in Lighting Systems.

When the cruise control on/off switch is turned OFF, the Cruise Control System will disengage.

The Cruise Control System will disengage when the ECM detects that a driver override function has been active for approximately 60 seconds.

When Cruise Control System has been disengaged, the ECM 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 ECM will be erased when the Off button is activated, or the ignition switch is turned OFF.

Cruise Control Inhibited
The engine control module (ECM) 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 within 9-16 volts.
- The Traction Control System (TCS) is active for more than 2 seconds.