GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 4WD 🢒 Body and Accessories 🢒 Body Control System 🢒 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 function is malfunctioning by checking functions internally enabled by the BCM.

    2.

  2. The body control module (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 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

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

  1. Turn key to the ON position.
  2. Close all vehicle doors.
  3. Turn key to the OFF position.
  4. Attempt to operate all of the following functions that are equipped on the vehicle:
    5. • Sunroof (Trailblazer, Envoy, Bravada)
    • Right and left rear power windows (Trailblazer, Envoy, Bravada)
    • Right and left rear quarter power vent windows (Bravada)

Does RAP function properly for one or more of the above accessories?

Go to Control Module References in Body Control Systems for the applicable Diagnostic Systems Check for the system that does not operate

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

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.

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

Go to Step 4

Go to Power Mode Mismatch in Body Control System

4

  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 5

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

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 Diagnostic Trouble Code (DTC) List in Body Control Systems
    • B1004 Diagnostic Trouble Code (DTC) List in Body Control Systems
    • B1007 Diagnostic Trouble Code (DTC) List in Body Control Systems
    • B1009 Diagnostic Trouble Code (DTC) List in Body Control Systems
    • B1440 Diagnostic Trouble Code (DTC) List in Body Control Systems

Are any of the DTCs shown on the scan tool?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 8

8

Does the scan tool display DTC B1445?

Go to DTC B1445

Refer to Control Module References in Body Control Systems for the applicable sub-section/DTC procedure