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 avalible information before tests are performed.

  3. Tests for other subsystem malfunctions within the control module used by the Variable Effort Steering (VES) system.

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

NOTE: The BCM/ESC stores the DTCs scan tool data and special functions. However, the scan tool menu to access variable effort steering is located in chassis.

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the Electronic Suspension Control (ESC) Module, vehicles equipped with Real Time Damping (RTD), or the Body Control Module (BCM), vehicles W/O RTD.

Does the scan tool communicate with the ESC module, or BCM?

Go to Step 3

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

3

Select the ESC module, or BCM Display DTCs function on the scan tool.

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

Go to Diagnostic Trouble Code (DTC) List in Data Link Communications

Go to Step 4

4

Does the scan tool display any BCM, or RTD, if equipped DTCs?

Go to Diagnostic Trouble Code (DTC) List in Body Control System, or Diagnostic Trouble Code (DTC) List in Real Time Damping

Go to Step 5

5

Does the scan tool display any VES DTCs?

Go to Diagnostic Trouble Code (DTC) List

System OK