GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2003 🢒 Ascender - 4WD 🢒 Body and Accessories 🢒 Retained Accessory Power 🢒 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 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 all of the following functions that are equipped on the vehicle:
    5. • Radio/Audio System
    • Sunroof (Trailblazer, Envoy, Bravada)
    • Right and left rear power windows (Trailblazer, Envoy, Bravada)
    • Right and left rear quarter power vent windows (Bravada)

Are all of the functions inoperative?

Go to Step 2

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

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

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

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Retained Accessory Power

5

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 6

6

Compare the DTCs shown in the scan tool to the DTCs listed in Diagnostic Trouble Code (DTC) List in Body Control Systems.

Are any of the DTCs shown on the scan tool?

Go to the appropriate DTC diagnostic table

Refer to Symptoms - Retained Accessory Power