• | 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 | Short to Ground | High Resistance | Open | Short to Voltage |
---|---|---|---|---|
Vehicle Speed Signal | P0608 | 1 | P0608 | P0608 |
1. Speedometer Inaccurate or Inoperative. |
The engine control module (ECM) creates the vehicle speed output signal by pulsing the vehicle speed signal circuit to ground at a rate of 4 KPPM. The VSS signal circuit is pulled high to B+ in the instrument panel cluster (IPC). The IPC converts the 4 KPPM 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.
Instrument Cluster Description and Operation
Control Module References for scan tool information.
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. Verify the speedometer display matches the scan tool Vehicle Speed parameter in the ECM Engine Data List.
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.
⇒ | If the speedometer does not perform the IPC Gage Sweep Test, replace the IPC. |
⇒ | If the speedometer matches the scan tool Vehicle Speed parameter, test the signal circuit terminal F2 for a short to voltage, a short to ground or an open/high resistance. If circuit tests normal, replace the radio. |
⇒ | If the speedometer matches the scan tool Vehicle Speed parameter, test the signal circuit terminal 18 for a short to voltage, a short to ground or an open/high resistance. If circuit tests normal, replace the rear object sensor control module. |
⇒ | If the speedometer matches the scan tool Vehicle Speed parameter, test the signal circuit terminal 11 for a short to voltage, a short to ground or an open/high resistance. If circuit tests normal, replace the HUD. |
⇒ | 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. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM, IPC, HUD, radio and rear object sensor control module replacement, setup and programming