GM Service Manual Online
For 1990-2009 cars only

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

  2. The Symptom Table will determine the correct diagnostic procedure to use.

  3. 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 following:
  3. • The Instrument Panel Cluster (IPC)
    • The Body Control Module (BCM)

Does the scan tool communicate with the modules?

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 parameter in the Diagnostic Circuit Check menu on the scan tool.
  2. Rotate the ignition switch through all positions while observing the Class 2 Power Mode parameter.

Does the Class 2 Power Mode 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 display DTCs function on the scan tool for the following modules:

    • The IPC
    • The BCM

Does the scan tool display any DTCs?

Go to Step 5

Go to Symptoms - Wiper/Washer Systems

5

Does the scan tool display DTCs that begin with "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 DTCs B1656, B1657 or B1658?

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

Go to Step 7

7

Does the scan tool display DTCs B1982 or B1983?

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

Go to Symptoms - Wiper/Washer Systems