Speedometer and/or Odometer Inaccurate or Inoperative
Speedometer and/or Odometer Inaccurate or Inoperative
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) 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 End Views By Name)
Description and Operation
Instrument Cluster Description and Operation (Instrument Cluster)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
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 and Repair). 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 and Repair).
1. Ignition ON, with the scan tool installed, perform the IPC Gauge 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 Gauge 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 ECM.
7. Ignition ON, test for 9-11 volts between the vehicle speed signal circuit terminal 57 and ground.
• If less than the specified range, 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 the specified range, 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