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 |
DTC Descriptors
DTC B0608: Vehicle Speed Output CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
Vehicle Speed Signal Circuit | P0608 | P0608 | P0608 |
Circuit/System Description
The engine control module (ECM) creates the vehicle speed output signal by pulsing the vehicle speed signal circuit to ground at a rate of 4KPPM. The ECM monitors the voltage at the vehicle speed output signal circuit to determine when the voltage is out of the normal operating range. The instrument panel cluster (IPC) receives vehicle speed data from the ECM via the serial data circuit for display in the speedometer. The radio and the object detection module receive vehicle speed data via a discreet vehicle speed signal circuit from the ECM. The radio and the object detection module use the 4KPPM vehicle speed signal from the ECM to determine vehicle speed.
Conditions for Running the DTC
| • | The engine speed is more than 400 RPM. |
| • | The ignition voltage is between 9-18 volts. |
Conditions for Setting the DTC
| • | The ECM detects that the commanded state of the driver and the actual state of the signal circuit do not match |
| • | The above condition must be present for a minimum of 5 seconds. |
Action Taken When the DTC Sets
The ECM records the operating conditions at the time the diagnostic fails. The ECM displays the failure information in the Failure Records on the scan tool.
Conditions for Clearing the DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The history DTC clears after 40 malfunction-free warm-up cycles. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Instrument Cluster Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References 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. Verify that 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.
- Ignition OFF, disconnect the harness connector at the rear object sensor control module.
- With the drive wheels raised start the engine and place the vehicle transmission 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.
- Ignition OFF disconnect the X1 harness connector at the engine control module.
- Ignition ON, test for 9-11 volts between the vehicle speed signal circuit terminal 39 and ground.
- If all circuits test normal, test or replace the ECM.
| ⇒ | If the speedometer matches the scan tool Vehicle Speed parameter, test the vehicle speed signal circuit terminal 18 for a short to voltage, a short to ground or an open/high resistance. If the circuit tests normal, replace the rear object sensor control module. |
| ⇒ | 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 radio. |
| ⇒ | If greater than 11 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the radio. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM, radio and the object detection module replacement, setup and programming
