Test Description

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

1. This step verifies that the RAP power mode function is malfunctioning by checking functions internally enabled by the BCM.

3. The BCM sends class 2 messages to other control modules via the serial data link, allowing them to operate in RAP power mode. Lack of communication may be due to a partial malfunctions of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

4. This step is checking for DTCs in the BCM.

5. The presence of DTCs which begin with "U" indicate that other module is not communicating. The specified procedure will compile all the available information before tests are performed.

Fig 1: Diagnostic System Check - Retained Accessory Power

Courtesy of GENERAL MOTORS CORP.