GM Service Manual Online
For 1990-2009 cars only

Review the system operation in order to familiarize yourself with the system functions. Refer to Automatic Level Control Description and Operation .

Before diagnosing any Automatic Level Control (ALC) System symptoms, perform the ALC self-test. The ALC self-test will test the system operation and display any current fault codes. Refer to Diagnostic Trouble Code (DTC) Displaying for instructions on activating the self-test and displaying fault codes.

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the ALC system. Refer to Checking Aftermarket Accessories .
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

Automatic Level Control Inflator Fill Valve Inoperative