Cruise Control Description and Operation (Conventional Cruise Control): Notes

WARNING: This page is about a different car, the 2009 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

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 rear integration module (RIM)
The cruise control cancel switch
The instrument panel module (IPM)
The cruise control 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)

The instrument panel module (IPM) monitors the signal circuit of the cruise control switches. The IPM send the cruise control switch status to the engine control module (ECM) via the GMLAN serial data circuit. The ECM uses the status of the cruise control switch to determine when to capture and maintain the vehicle speed. The ECM monitors the vehicle speed signal circuit in order to determine the desired 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 for the 3.6L engine, Throttle Actuator Control (TAC) System Description for the 4.4L engine or Throttle Actuator Control (TAC) System Description for the 4.6L engine.

Ignition voltage is supplied to the cruise control switch from the 2-ampere RUN/CRANK ELEC fuse located in the integrated IPM 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 IPM 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 IPM sends a GMLAN serial data message to the ECM indicating that the on/off switch is active. Similarly, when the normally open + RES switch or the normally open - SET switch are pressed, the switch closes and the IPM detects the predetermined voltage signal on the cruise control resume/accel and set/coast switch signal circuit. The IPM sends a GMLAN serial data message to the ECM indicating that the + RES switch or the - SET switch is active. The + RES switch or the - SET switch will remain inactive when the IPM has not received the predetermined voltage signal from the on/off switch.