P0608

DTC P0608

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using the 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.

DTC Descriptor
DTC P0608
^ Vehicle Speed Output Circuit

Diagnostic Fault Information





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

* Instrument Cluster Schematics (Instrument Cluster Schematics)
* Engine Controls Schematics ([1][2]Electrical Diagrams) for the 4.2L engine
* Engine Controls Schematics ([1][2]Electrical Diagrams) for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engines

Connector End View Reference

Component Connector End Views (Component Connector End Views)
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 (Control Module References) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector X1 at the ECM/PCM. Install a signal generator and instrument panel tester between the following vehicle speed signal circuit and ground:

* Terminal 21 (4.2L)
* Terminal 39 (5.3L/6.0L)

2. Ignition ON, set the signal generator to generate a speedometer signal. Verify that the vehicle speedometer indicates a reading.

• 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 instrument panel cluster (IPC).

3. If all circuits test normal, test or replace the ECM/PCM.

Repair Instructions

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

Control Module References (Control Module References) for the ECM/PCM and IPC replacement, setup, and programming