GM Service Manual Online
For 1990-2009 cars only

Diagnostic Fault Information

Important: Always perform the Diagnostic System Check - Vehicle

Circuit/System Description

This diagnostic procedure applies to serial data gages located in the instrument panel cluster (IPC) which include the speedometer, tachometer, engine coolant temperature gage and volt gage if equipped.

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

    •  Instrument Panel, Gages, and Console Connector End Views
    •  Inline Harness Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs
    •  Lifting and Jacking the Vehicle

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

Important: If the suspect gage is the speedometer, the drive wheels of the vehicle must be raised and the transmission must be placed in drive or first gear.

  1. Ignition ON, with the scan tool, perform the IPC Gage Sweep Test in the IPC Output Controls. Verify that all gage dials move from minimum to the maximum value and back to the gage minimum value.
  2. If the gage does not perform the IPC Gage Sweep Test, replace the IPC.
  3. Start the engine, with the vehicle drive wheels raised and place the transmission in drive or first gear. Verify that the speedometer value matches the scan tool Vehicle Speed parameter in the ECM Engine Data List.
  4. If the speedometer is incorrect, test or replace the IPC.

Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the IPC replacement, setup and programming.