Cruise Control System Diagnosis

Depending on the cruise control complaint, the PCM DTCs that would affect cruise operation mentioned in "Cruise Control System Operation" should be diagnosed and corrected first. If no DTCs exist, but a cruise control system problem does, the "Cruise Control System Check" chart should be the starting point. This will either locate the problem or will refer to a chart which will aid in diagnosis.

The Scan tool can be used to help diagnose an inoperative cruise control system or other faults related to the system. The Scan tool displays CRUISE ENABLED, a PCM commanded state which allows cruise to operate. The Scan tool also displays CRUISE ENGAGED, an actual feedback which tells the PCM the cruise control module is taking control of vehicle speed. When the cruise control module is taking control of vehicle speed, it will supply a ground to circuit 396 and CRUISE ENGAGED on Scan tool will display YES. The Scan tool can also display the stop lamp switch status for automatic transaxles or the cruise clutch switch status for manual transaxles as CRUISE BRAKE/CLUTCH SW.

With the vehicle in park and the engine running, CRUISE ENABLED and CRUISE ENGAGED should read NO on Scan tool. With the cruise control set, CRUISE ENABLED and CRUISE ENGAGED should read YES. If CRUISE ENABLED still reads NO when the cruise is attempting to be set, the PCM is not allowing cruise and that condition should be diagnosed first. If CRUISE ENGAGED continues to read NO on Scan tool when the cruise is attempting to be set, the cruise control module cannot control vehicle speed and that condition should be diagnosed next.

IMPORTANT:
^ An open or short to ground in the cruise engage input circuit will not affect cruise operation. However, a short to voltage will cause an inoperative cruise control system. CRUISE ENGAGED on Scan tool would always read NO if a short to voltage condition occurs. This Scan tool feedback will only update with the engine running.
^ The cruise control module will not allow cruise operation if the cruise enable input circuit is always low. The cruise control module must detect ignition voltage anytime the vehicle is traveling less than 32 km/h (20 mph). If the cruise control module detects a low voltage state when vehicle speed is below 32 km/h (20 mph), it will not engage cruise for the rest of the ignition cycle even if the fault corrects itself. NOTE: CRUISE ENABLED on Scan tool displays the PCM commanded state, not a feedback state.