Cruise Control System Diagnosis

Circuit Description
The Cruise Control system is a speed control system that maintains a desired vehicle speed under normal driving conditions. The cruise control system has the capability of the following:
^ Cruise
^ Coast
^ Resume speed
^ Accelerate
^ Raise (Tap-up) the vehicle speed by 1.6 km/h (1 mph)
^ Lower (Tap-down) the vehicle speed by 1.6 km/h (1 mph)

The PCM controls the cruise system. When the cruise control switch is in the ON position and you push the cruise SET/COAST switch, the PCM maintains the current vehicle speed. If the engine load varies, the PCM commands the throttle blade to the appropriate position in order to maintain the desired vehicle speed. The TAC Module sends all cruise control requests to the PCM via the serial data circuit. The cruise control system consists of the following components:
^ The Powertrain Control Module (PCM)
^ The Throttle Actuator Control (TAC) Module
^ The Throttle Actuator Control Motor
^ The Cruise Control Actuator Lever

Conditions for Enabling the Cruise System
^ The Cruise switch is in the ON position.
^ Ignition voltage is present to the cruise actuator lever.
^ The vehicle speed is greater than 39 km/h (24 mph).
^ The clutch or brake pedal is not depressed.
^ The transmission is in a forward gear.
^ The vehicle is not in a traction control event.
^ The engine is not in Engine Coolant Over Temperature-Fuel Disabled mode.
^ The cruise SET/COAST switch has been pushed and released.

Conditions for Disabling the Cruise System
^ The Cruise switch is turned to the OFF position.
^ Ignition voltage is interrupted to the cruise actuator lever.
^ The vehicle speed is less than 32 km/h (20 mph).
^ The clutch or brake pedal is depressed.
^ The engine is in Engine Coolant Over Temperature-Fuel Disabled mode.
^ The transmission is placed into neutral.
^ A concern with the clutch or brake pedal switches or circuits that the TAC module interprets as the pedal is applied.

Diagnostic Aids

Important:
^ Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter kit J 35616-A. Using this kit prevents damage to the harness/component terminals.
^ The following may cause an intermittent:
- Inspect for poor connections.
- Corrosion
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
^ Use the scan tool in order to monitor the Cruise Disengage History. This parameter lists the last 8 cruise disengage events.
^ The cruise control system disables for the current ignition cycle if an intermittent condition exists and DTC P0567 or DTC P0568 sets.
^ For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures