Speedometer and/or Odometer Inaccurate or Inoperative

Speedometer and/or Odometer Inaccurate or Inoperative

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



Diagnostic Fault Information






Circuit/System Description

The engine control module (ECM) creates the vehicle speed output signal by pulsing the circuit to ground at a rate of 4KPPM. The VSS input is pulled high to B+ in the instrument panel cluster (IPC). The IPC converts the 4KPPM vehicle speed signal to a speedometer position to indicate the vehicle speed. The ECM monitors the voltage at the vehicle speed output signal circuit to determine when the voltage is out of the normal operating range.


Reference Information
Schematic Reference

Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Instrument Cluster Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning)


Circuit/System Verification

Start the engine with the scan tool installed, the vehicle drive wheels raised and the transmission placed in drive or the first gear. Refer to Lifting and Jacking the Vehicle (Service Intervals) . Verify the speedometer display matches the scan tool Vehicle Speed parameter in the ECM Engine Data List.


Circuit/System Testing

Important: 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 (Service Intervals) .



1. Ignition ON, with the scan tool installed, perform the IPC Gage Sweep Test in the IPC Output Controls. Verify the speedometer dial moves from the minimum to the maximum position and back to the speedometer minimum position.

• If the speedometer does not perform the IPC Gage Sweep Test, replace the IPC.

2. Ignition OFF, disconnect the X2 harness connector at the radio.
3. Start the engine, with the drive wheels raised and the vehicle placed in drive or the first gear. Verify that the speedometer value does not match the scan tool Vehicle Speed parameter in the ECM Engine Data List.

• If the speedometer matches the scan tool Vehicle Speed parameter, test the vehicle speed signal circuit terminal D for a short to voltage, a short to ground or an open/high resistance. If the circuit tests normal, replace the radio.

4. Ignition OFF, disconnect the harness connector at the head-up display (HUD).
5. Start the engine, with the drive wheels raised and the vehicle placed in drive or the first gear. Verify that the speedometer value does not match the scan tool Vehicle Speed parameter in the ECM Engine Data List.

• If the speedometer matches the scan tool Vehicle Speed parameter, test the vehicle speed signal circuit terminal 3 for a short to voltage, a short to ground or an open/high resistance. If circuit tests normal, replace the HUD.

6. Ignition OFF, disconnect the X1 harness connector at the engine control module.
7. Ignition ON, test for 9-11 volts between the vehicle speed signal circuit terminal 57 and ground.

• If less than 9 volts, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC.


• If greater than 11 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the IPC.

8. If all circuits test normal, test or replace the ECM.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning) for the ECM, IPC, HUD and radio replacement, setup and programming