Cruise Control Clutch Output Circuit Low Voltage
Circuit Description
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 the 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 P1587 sets when the cruise control clutch is commanded Off and the feedback voltage at the PCM is low.
Conditions for Setting the DTC
DTC P1587 will set if the cruise control clutch feedback voltage is less than 1.25 volts with the cruise control clutch commanded Off when:
| • | The condition exists for longer than 500 milliseconds. |
| • | The ignition is On. |
DTC P1587 diagnostic runs continuously with the ignition On and the cruise control clutch commanded Off.
DTC P1587 is a type D DTC.
Diagnostic Aids
To locate an intermittent problem, use the scan tool to monitor the C/C CLUTCH - LOW VOLT or C/C CLUTCH - OPEN test with ignition On, the engine Off. When a fault (an open or a short to ground) exists, the scan tool will display TEST FAIL for both tests.
The tests will fail only when the device is being commanded Off and the voltage at the PCM is low. The tests update every 100 ms whenever the ignition is turned On and the device is being commanded Off via the scan tool or the PCM.
Loss of cruise control module ground can also set this DTC. If this condition exists, DTC P1581 and P1583 will also set.
Loss of cruise control module ignition voltage can also set this DTC.
