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

Ignition 1 voltage is supplied directly to the malfunction indicator lamp (MIL). The engine control module (ECM) turns the MIL ON by sending a request to the instrument panel cluster (IPC) via the CAN communication circuit. The MIL should be on steady with the ignition ON and the engine OFF. When the engine is started, the MIL should turn OFF.

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Displays and Gages Connector End Views

Description and Operation

Instrument Cluster Description and Operation

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
    •  Scan Tool Output Controls

Circuit/System Verification

  1. Ignition ON, verify that the following diagnostic trouble codes (DTCs) are not set: U0100, U0155, U2105.
  2. If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
  3. Command the MIL ON and OFF with a scan tool. The MIL should respond to the scan tool commands.
  4. If the MIL does not respond properly, replace the IPC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for Instrument Panel Cluster replacement, setup, and programming