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.

  3. The presence of DTCs which pertain to the ABS/TCS system must be diagnosed first. The specified procedure will compile all the available information before tests are performed.

  4. The presence of DTCs which pertain to the transaxle must be diagnosed after any ABS/TCS codes. 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 Powertrain Control Module and the Electronic Brake Control Module.

Does the scan tool communicate with the Powertrain Control Module and the Electronic Brake Control Module?

Go to Step 3

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

3

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 4

4

Select the ABS Control Module display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Diagnostic Trouble Code (DTC) List in Antilock Brake System

Go to Step 5

5

Select the Powertrain Control Module display DTCs function on the scan tool.

Does the scan tool display any transaxle DTCs?

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

Go to Step 6

6

Select the Powertrain Control Module display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Diagnostic Trouble Code (DTC) List

Go to Symptoms - Cruise Control