Cruise Control: Description and Operation

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at vehicle 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 Powertrain Control Module (PCM)
^ The On/Off switch
^ The Resume/Accel. Switch
^ The Set/Coast Switch
^ The TCC/Brake Switch
^ The Throttle Actuator Control (TAC) module

Cruise Control Engaged
The PCM will engage and adjust vehicle speed based on the information received from the TAC module via the serial data link. The TAC module monitors the signal circuits of the following cruise control switches:
^ On/Off
^ Resume/Accel.
^ Set/Coast

The cruise control switches are located on the multifunction/turn signal lever.

Ignition positive voltage is supplied from the 10 ampere CRUISE fuse, to the cruise control switch. When the cruise control On/Off switch is in the On position, the TAC module detects a high signal voltage on the cruise on switch signal circuit. When the Set/Coast button is pressed, the TAC module detects a high signal voltage on the set/coast signal circuit. In order to engage the cruise control system, the On/Off switch must be in the On position and the Set button momentarily pressed. The TAC module communicates with the PCM, in order to confirm that the cruise control enable criteria has been met. The PCM will also record the selected vehicle speed. When the Resume/Accel. switch is pressed, the TAC module detects a high signal voltage on the resume/accel switch signal circuit. Pressing the Resume switch will recall the previous selected vehicle speed that is recorded in the PCM. Pressing the Accel. switch will allow the vehicle to accelerate to a vehicle speed greater than the current set vehicle speed. When the Accel. switch is released, the vehicle speed will decrease to the current set vehicle speed. Pressing the Coast switch will allow the vehicle speed to decrease from the current set without deactivating the cruise control system. When the Coast switch is released, the vehicle will accelerate to the current set vehicle speed.

Cruise Control Disengaged
The PCM disengages the cruise control operation based on the information received from the TAC module via the serial data link. The TAC module monitors the signal circuits of the following switches:
^ The On/Off switch
^ The TCC/Brake Switch

The TCC/Brake switch is used to disengage the cruise control. The TCC/Brake switch is mounted to the brake pedal bracket. Pressing the brake pedal while the cruise control is engaged will disengaged the cruise control system. When the brake pedal is pressed, the normally open TCC/Brake switch closes and the TAC module detects a low signal voltage on the TCC/Brake signal circuit. The vehicle speed stored in the memory of the PCM will be erased when the Off button is pressed, or the ignition switch is turned off.

Cruise Control Inhibited
The PCM inhibits the cruise control operation when any of the following conditions exist:
^ The vehicle speed is less than 40 km/h (25 mph).
^ The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
^ The engine RPM low.
^ The engine RPM is high, with fuel cut-off.
^ The vehicle speed is to high.
^ The battery is either overcharged or undercharged.
^ The antilock brake system/traction control system is active for more than 2 seconds.