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

This diagnostic procedure applies to serial data gages located in the instrument panel cluster (IPC) which includes the speedometer and tachometer.

Reference Information

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component 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

Control Module References for scan tool information

Circuit/System Verification

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. Refer to Lifting and Jacking the Vehicle.

  1. Ignition ON and the scan tool installed, perform the IPC Engine Speed Control Test from the ECU Control menu. Verify that the tachometer pointer moves from the minimum value to the maximum value as commanded.
  2. If the tachometer does not perform the Engine Speed Control Test, test or replace the IPC.
  3. Perform the IPC Vehicle Speed Control Test from the ECU Control menu. Verify that the speedometer pointer moves from the minimum value to the maximum value as commanded.
  4. If the speeometer does not perform the Vehicle Speed Control Test, test or replace the IPC.
  5. 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.
  6. If the speedometer is incorrect, test or replace the IPC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the IPC replacement, setup and programming