GM Service Manual Online
For 1990-2009 cars only

Important: Review the system operations in order to familiarize yourself with the system functions. Refer to Two Speed Rear Axle Shift System Description and Operation in Rear Drive Axle and Locking Differential Description and Operation .

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the Rear Axle Control System. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
    • Inspect the rear axle for the proper fluid level.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Always check wiring connections and retest the suspect circuit before replacing components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

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

    •  Differential Lock Indicator Inoperative
    •  Differential Lock On at All Times
    •  Differential Lock Inoperative
    •  Two Speed Rear Axle Inoperative in Rear Drive Axle