B1477

DTC B1477

CIRCUIT DESCRIPTION
The retained accessory power (RAP) function allows selected vehicle functions to operate for 10 minutes after the ignition switch is turned OFF. The body control module (BCM) monitors the ignition switch position, the door jamb switches and the voltage on the RAP relay control circuit. The BCM will command the RAP relay on by grounding the RAP relay control circuit when all the doors are closed and the ignition switch is switched from ON to the OFF position.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC B1477 Retained Accessory Power Circuit Low
- DTC B1478 Retained Accessory Power Circuit High

CONDITIONS FOR RUNNING THE DTC
The system voltage must be between 9-16 volts.

CONDITIONS FOR SETTING THE DTC
- DTC B1477:
- The BCM detects a short to ground or an open in the RAP relay control circuit when the RAP relay is not energized.
- The condition above must be present for more than 1 second.
- DTC B1478:
- The BCM detects a short to battery in the RAP relay control circuit when it tries to energize the RAP relay.
- The condition above must be present for more than 1 second.

ACTION TAKEN WHEN THE DTC SETS
- DTC B1477:
- The BCM stores DTC B1477 in memory.
- The circuits powered by the RAP relay will not operate if the RAP relay control circuit is open.
- The circuits powered by the RAP relay remain powered at all times if the RAP relay control circuit is shorted to ground.
- DTC B1478:
- The BCM stores DTC B1478 in memory.
- The RAP relay can not be energized.

CONDITIONS FOR CLEARING THE DTC
- A current DTC clears when the malfunction is no longer present.
- A history DTC clears when the ignition has been cycled 100 times, without a repeat of the malfunction.

DIAGNOSTIC AIDS
If the DTC B1477 or B1478 is a history DTC, the fault may be intermittent.

The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to ground or to battery in the RAP relay control circuit.
- The RAP relay coil is shorted to ground or to battery internally.
- The BCM is shorted to ground or to battery internally.

TEST DESCRIPTION

Steps 1-10:

The numbers below refer to the step numbers on the diagnostic table.
2. During the RAP relay operation, listen for an audible click. Command the ON and the OFF states. Repeat the commands as necessary.
3. This step verifies whether the RAP relay has a defect.
4. This step tests the supply voltage circuit to the RAP relay coil.
5. This step tests the control circuit of the RAP relay.