Test Description

WARNING: This page is about a different car, the 2004 Cadillac Seville. However, it is still accessible from the selected car via links, so may be relevant.

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

2: 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.
4: 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.

Diagnostic System Check - Automatic Level Control

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	Turn ON the ignition, with the engine OFF. Attempt to establish communication with the following modules: Electronic Suspension Control (ESC) Module Electronic Brake Control Module (EBCM) Powertrain Control Module (PCM) Does the scan tool communicate with all of the listed control 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. Access the Ignition Switch parameter in the body control module (BCM) inputs data display list. 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
4	Select the display DTCs function on the scan tool for the following modules: Electronic Suspension Control (ESC) Electronic Brake Control (EBCM) Powertrain Control (PCM) Does the scan tool display any DTCs?	Go to Step 5	Go to Symptoms - Automatic Level Control
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 any PCM DTCs?	Go to Diagnostic Trouble Code (DTC) List in Engine Controls	Go to Step 7
7	Does the scan tool display any EBCM DTCs?	Go to Diagnostic Trouble Code (DTC) List in ABS Traction Control	Go to Step 8
8	Does the scan tool display any of the following DTCs? C0657, C0658, C0662, C0663	Go to Diagnostic Trouble Code (DTC) List	Go to Diagnostic Trouble Code (DTC) List in Electronic Suspension Control