GM Service Manual Online
For 1990-2009 cars only

The body control module (BCM) controls the retained accessory power (RAP) feature. The BCM controls devices by directly supplying power through the RAP relay, or by a class 2 command through the instrument panel cluster (IPC). The RAP relay allows the BCM to directly control the application of power to the following devices:

    • Power windows
    • Rear quarter windows

The IPC monitors the RAP relay control circuit and sends class 2 RAP commands to the following devices:

    • Radio
    • Vehicle interface unit (VIU), if equipped

The BCM feature allows for the operation of the above components for 10 minutes, or until a vehicle door opens, after the ignition switch turns from the RUN to the OFF position.

When the ignition switch is in either of the following positions, the BCM energizes the RAP relay by grounding the relay control circuit:

    • ACC
    • RUN

The BCM turns OFF the RAP relay when the ignition switch is in the START position, thus disabling the RAP feature during the engine crank and bulb test.

When the ignition switch turns from the RUN position to the OFF position with all of the vehicle doors closed, the BCM leaves the RAP relay energized for 10 minutes if the vehicle has been driven for more than 15 miles, or until 1 or more of the following conditions are met:

    • Any vehicle door opens.
    • The content theft deterrent system goes into the armed mode if equipped with Content Theft Deterrent System - RPO UA6.

The BCM resets the RAP timer when the ignition switch turns from the OFF position to the ACC position.

Diagnostic Aids

The body control module (BCM) monitors the retained accessory power (RAP) relay control circuit. The BCM sets the DTC 004 when detecting the following conditions:

    • A short to B+ in the relay control circuit
    • A short to ground in the relay control circuit

If the power windows operate properly under RAP conditions and the radio or vehicle interface unit (VIU) do not operate properly, the condition exists in the class 2 circuit of the radio, VIU, or instrument panel cluster (IPC). Refer to Scan Tool Does Not Communicate with Class 2 Device .