GM Service Manual Online
For 1990-2009 cars only

Test Description

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

  1. 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.

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

Step

Action

Yes

No

1

Install a scan tool.

Does the scan tool power up?

Go to Step 2

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

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the body control module (BCM).

Does the scan tool communicate with the BCM?

Go to Step 3

Go to Scan Tool Does Not Communicate with Class 2 Device 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

    • Select the body control module display DTCs function on the scan tool.
    • Select the seat and mirror control module display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Doors

5

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

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

Go to Step 6

6

Does the scan tool display DTC B1000?

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

Go to Step 7

7

Does the scan tool display DTC B1477 or B1478?

Go to Diagnostic Trouble Code (DTC) List in Retained Accessory Power

Go to Step 8

8

Does the scan tool display DTCs beginning with a P code?

Go to Diagnostic Trouble Code (DTC) List in Engine Controls

Go to Step 9

9

Does the scan tool display one of the following DTCs?

    • DTC B1349
    • DTC B1560
    • DTC B1565
    • DTC B1570
    • DTC B1575
    • DTC B1580
    • DTC B1590
    • DTC B1600
    • DTC B1605
    • DTC B1610
    • DTC B1620
    • DTC B1630
    • DTC B1635
    • DTC B3069
    • DTC B3270
    • DTC B3272

Go to Diagnostic Trouble Code (DTC) List

Go to Symptoms - Doors