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P0608




DTC P0608

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptor
DTC P0608
- Vehicle Speed Output Circuit

Diagnostic Fault Information





Circuit/System Description

The vehicle speed signal circuit is an input to the throttle actuator control (TAC) module from the powertrain control module (PCM). The PCM provides a constant voltage signal on the vehicle speed signal circuit. The PCM creates the vehicle speed signal by internally pulsing the vehicle speed signal to ground. The TAC module uses the vehicle speed signal from the PCM, in order to determine the vehicle speed. The TAC module then sends a serial data message to the PCM indicating the vehicle speed that the TAC module has detected.

Conditions for Running the DTC

* The vehicle is in Drive or Reverse.
* The vehicle speed is greater than 8 km/h (5 mph).
* There are no current VSS DTCs present.
* The ignition voltage is between 9-16 volts.

Conditions for Setting the DTC

* The PCM sends a 8 km/h (5 mph) signal on the vehicle speed signal circuit to the TAC module. The TAC module sends a serial data message to the PCM indicating that the vehicle speed is 0 km/h (0 mph).
* The above condition is present for greater than 4 seconds.

Actions Taken When the DTC Sets

* The cruise control system is disabled.
* The malfunction indicator lamp (MIL) will illuminate.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.
* A history DTC will clear after 40 malfunction-free ignition cycles have occurred.

Reference Information
Schematic Reference

* Cruise Control Schematics (Electrical Diagrams)
* Exterior Lights Schematics (Exterior Lights Schematics)

Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cruise Control Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the TAC module.
2. Ignition ON, test for 8.0-9.0 volts between the signal circuit terminal 4 and ground.

If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the PCM.
If less than the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.

3. If all circuits test normal, replace the TAC module.

Repair Instructions

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

Control Module References (Programming and Relearning) for PCM or TAC module replacement, setup, and programming