GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Express - AWD 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Diagnostic System Check - Retained Accessory Power

Test Description

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.

    2.

  2. 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 malfunction 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.

    3.

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

    4.

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

Step

Action

Yes

No

Schematic Reference: Retained Accessory Power (RAP) Schematics

1

  1. Turn key to the ON position.
  2. Close all vehicle doors.
  3. Turn key to the OFF position.
  4. Attempt to operate the Right and Left Power Window controls.

Does the RAP function normally for either window?

Go to Diagnostic System Check - Door Systems in Doors

Go to Step 2

2

Install a scan tool.

Does the scan tool power up?

Go to Step 3

Go to Scan Tool Does Not Power Up in Data Link Communications

3

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate the BCM.

Does the scan tool communicate with the BCM?

Go to Step 4

Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications

4

Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.

  1. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
  2. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control Systems, for a list of the power mode states that correspond to each ignition switch position.

Does the ignition switch parameter reading match the ignition switch position for all switch positions?

Go to Step 5

Go to Power Mode Mismatch in Body Control System

5

Select the body control module display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Step 6

Go to Symptoms - Retained Accessory Power

6

Does the scan tool display any DTCs which begin with a "U"?

Go to Diagnostic Trouble Code (DTC) List in Data Link Communications

Go to Step 7

7

Compare the DTCs listed below to the scan tool:

    • B1000 in Body Control System
    • B1420 in Body Control System
    • B1440 in Body Control System
    • B1480 in Lighting Systems
    • B1477 or B1478 in Retained Accessory Power

Are any of the DTCs shown on the scan tool?

Go to the appropriate DTC diagnostic table

Go to Diagnostic Trouble Code (DTC) List in Body Control Systems for the applicable sub-section/DTC procedure