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Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 775 (Retained Accessory Power System) >> Diagnostic Information and Procedures >> DTC B1478: Short To Battery Or Open In RAP Relay Control Feed Circuit >> Circuit Description
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Circuit Description

WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

The body control module (BCM) controls the retained accessory power (RAP) feature. The RAP feature allows the following components to operate for 10 minutes, or until a vehicle door opens, after the ignition switch turns from RUN or ACC to LOCK:

The BCM interfaces with the vehicle's power distribution system through the RAP relay. The RAP relay allows the BCM to control the application of power to the RAP controlled feed circuit. When the ignition switch is in either the ACC or the RUN position, the BCM energizes the RAP relay by powering the RAP relay control feed circuit.

The BCM turns off the RAP relay when the ignition switch is in the START position. The RAP feature therefore disables during engine crank and bulb test.