B1478

CIRCUIT DESCRIPTION
The retained accessory power (RAP) function allows selected vehicle functions to operate 20 minutes after the ignition switch is turned OFF. The 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.

CONDITIONS FOR RUNNING THE DTCs B1477 and B1478
- The system voltage must be between 9.0-16.0 volts.
- The doors must be closed.
- The ignition switch must be cycled from ON to OFF.

CONDITIONS FOR SETTING THE DTC
- When the BCM detects battery voltage or the RAP relay control circuit with the ignition switch in the RUN position.
- BCM detects battery voltage when RAP is commanded OFF.
- The above conditions must be met for 0.5 seconds.

ACTION TAKEN WHEN THE DTC SETS
The following items will not function:
- The front and rear radio
- The power windows
- The sunroof
- The driver information center
- The VIU

CONDITIONS FOR CLEARING THE DTC
- A current DTC clears when the malfunction is no longer present.
- A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

DIAGNOSTIC AIDS
Perform a visual inspection of the wiring, the terminals and the connectors.

Refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-4:

Steps 5-11:

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the RAP relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
3. Tests for battery voltage at the coil side of the RAP relay. The RAP fuse supplies power to the coil side of the RAP relay.
4. Verifies that the BCM is providing ground to the RAP relay.
5. Tests if ground is constantly being applied to the RAP relay.
10. After replacement of the BCM you must calibrate the new module for proper operation.