The cruise control clutch is used to engage the cruise control motor to the cruise control module attachment rod mechanism. The powertrain control module (PCM) controls the cruise control clutch by pulling the cruise control clutch circuit to ground. The cruise control module internally supplies the internal clutch ignition voltage through a driver circuit. In order for the driver circuit to supply ignition voltage to the clutch, ignition voltage must be present at the cruise/brake input of the cruise control module. When the brake pedal is depressed (switch opens, input goes low), the PCM opens the clutch ground circuit and the cruise control module opens the clutch ignition voltage circuit. The cruise control module also supplies ignition voltage on the cruise control clutch circuit through a resistor even when the brake pedal is depressed. This voltage cannot turn the clutch On, however. The PCM monitors the cruise control clutch circuit for low and high voltage faults. DTC P1588 sets when the cruise control clutch is commanded On and the feedback voltage at the PCM is high.

DTC P1588 will set if the cruise control clutch feedback voltage is greater than 1.25 volts with the cruise control clutch commanded On when:

DTC P1588 diagnostic runs continuously with the engine running and the cruise control clutch commanded On.

DTC P1588 is a type D DTC.

To locate an intermittent problem, use the scan tool to command the CRUISE CONTROL CLUTCH On, while monitoring the C/C CLUTCH - HIGH VOLT test. When a fault (a short to voltage or a shorted cruise control clutch) exists, the scan tool will display TEST FAIL.

The test will fail only when the device is being commanded On and the voltage at the PCM is high. The test updates every 100 ms whenever the ignition is turned On and the device is being commanded On via the scan tool or the PCM.