DTC Descriptor
DTC P0608: Vehicle Speed Output CircuitDiagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Vehicle Speed Signal Circuit | P0608 | P0608 | P0608 | -- |
Circuit Description
The engine control module (ECM)/powertrain control module (PCM) creates the vehicle speed output signal by pulsing the circuit to ground. The ECM/PCM monitors the voltage on the vehicle speed output circuit. If the ECM/PCM determines that the voltage is out of the normal operating range, a DTC sets.
Conditions for Running the DTC
| • | The engine speed is more than 400 RPM. |
| • | The ignition voltage is between 6-18 volts. |
Conditions for Setting the DTC
| • | The ECM/PCM 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/PCM records the operating conditions at the time the diagnostic fails. The ECM/PCM displays the failure information in the Failure Records on the scan tool.
Conditions for Clearing the MIL/DTC
| • | The history DTC clears after 40 malfunction-free warm-up cycles. |
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | The ECM/PCM receives the clear code command from the scan tool. |
Reference Information
Schematic Reference
| • | Engine Controls Schematics for the 4.2L engine |
| • | Engine Controls Schematics for the 5.3L engine |
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the ECM/PCM. Install a signal generator and instrument panel tester between the vehicle speed signal circuit and ground.
- Ignition ON, set the signal generator to generate a speedometer signal. Verify that the vehicle speedometer indicates a reading.
- If all circuits test normal, test or replace the ECM/PCM.
| ⇒ | If no speedometer reading is present, test the signal circuit for an open/high resistance, a short to voltage, or a short to ground. If the circuit tests normal, replace the IPC. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM/PCM and IPC replacement, setup, and programming
