GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The instrument panel cluster (IPC) illuminates the AWD Disabled indicator by supplying ground to the lamp. The rear differential clutch control module (CCM) sends a serial data messages to the IPC, in order to command the indicator ON or OFF.

Diagnostic Aids

    • If the AWD disabled lamp turns Off, and there are no DTCs stored in any other vehicle systems, the CCM may detected incorrect size tires installed on the vehicle, or over-heating of the AWD coupling.
    • For incorrect tire size, check tire pressure, size and brand. All tires must have the same diameter to protect the AWD coupling.
    • For overheating, monitor the temperature of the AWD coupling in the scan tool and, if the temperature stays above 70 degrees C and condition for the size are correct, replace the CCM.

Reference Information

Schematic Reference

All-Wheel Drive Schematics

Connector End View Reference

Transfer Case Control Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Testing

Important: Diagnose all vehicle DTCs before using this diagnostic.

With the scan tool, select instrument panel special functions Lamp Test. Command the instrument panel warning lamps OFF.

If the AWD Disabled warning lamp does not turn OFF, replace the IPC.
If the AWD Disabled lamp turns OFF and there are no DTCs stored in any vehicle systems, replace the CCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for CCM or IPC replacement, setup, and programming.