GM Service Manual Online
For 1990-2009 cars only

Strategy Based Diagnostics

Review the system operations in order to familiarize yourself with the system functions. Refer to Differential Carrier Assembly Disassembled Views and Differential Carrier Assembly Description and Locking Differential Description and Operation in Drive Axle - Locking/Limited Slip and Transfer Case Description and Operation in Transfer Case - Steyr. All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostic flow may always be used in order to resolve a system condition. The diagnostic flow is the place to start when repairs are necessary. For a detailed explanation, refer to Strategy Based Diagnosis in General Information.

Visual/Physical Inspection

    • Inspect for aftermarket devices, which could affect the operation of the vehicle. 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.
    • Check for the correct lubricant level and the proper viscosity.
    • Verify the exact operating conditions under which the concern exists. Note factors such as vehicle speed, road conditions, ambient temperature, and other specifics.
    • Compare the driving characteristics or sounds, if applicable, to a known good vehicle and make sure you are not trying to correct a normal condition.
    • Inspect for all-wheel drive activation and operation. Refer to All-Wheel Drive (AWD) System Functional Inspection .
    • Factors that may contribute to an inoperative rear differential include:
       - Low gear oil levels
       - Differential inoperative due to antilock brake system (ABS) function
       - Inoperative powertrain control module (PCM) and/or wiring system
       - A mini-spare or different size tire installed
       - A fluid over-temperature condition
       - An inoperative or "stuck" clutch pump check valve
       - A defective rear differential assembly
       - An inoperative transfer case assembly

Intermittent

Test the vehicle under the same conditions that the customer reported in order to verify the system is operating properly.

Symptom List

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

    •  Diagnostic Starting Point - Vibration Diagnosis and Correction in Vibration Diagnosis and Correction
    •  Diagnostic Starting Point - Locking/Limited Slip Rear Axle in Drive Axle - Locking/Limited Slip
    •  Diagnostic Starting Point - Wheel Drive Shafts in Wheel Drive Shafts
    •  All-Wheel Drive (AWD) System Functional Inspection
    •  Noisy in Drive
    •  Noisy When Coasting
    •  Intermittent Noise
    •  Constant Noise
    •  Noisy on Turns
    •  Rear Differential Carrier Leak Diagnosis