GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Canyon Pickup - 4WD 🢒 Body 🢒 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 retained accessory power (RAP) power mode is malfunctioning by checking functions enabled by the body control module (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 checks for DTCs in the BCM.

    4.

  4. The presence of DTCs which begin with "U" indicate that a control module is not communicating. Diagnose DTCs that begin with "U" before you diagnose any other DTCs.

Step

Action

Yes

No

Schematic Reference: Retained Accessory Power (RAP) Schematics

1

  1. Turn the ignition to the ON position.
  2. Close all of the vehicle doors.
  3. Turn the ignition to the OFF position.
  4. Attempt to operate the windshield wipers and all power windows.

Does the RAP function normally for the windshield wipers or for any power window?

Go to Diagnostic System Check - Wiper/Washer in Wipers/Washer System or 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 with the body control module (BCM) using the scan tool.

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 with 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, Body Control System Description and Operation for a list of the power mode states that correspond to each ignition switch position.

Does the scan tool display 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 BCM display DTCs function with 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

Does the scan tool display DTCs B1000, B1372, B1373, B1382, B1383, B1442, or B1443?

Go to Diagnostic Trouble Code (DTC) List in Body Control System

Go to Step 8

8

Does the scan tool display DTCs B1477 or B1478?

Go to DTC B1477 or B1478

Go to Symptoms - Retained Accessory Power