DTC P0608. Buick Lucerne 2009

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2009 🢒 Lucerne 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC P0608

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 Descriptor

DTC P0608: Vehicle Speed Output Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Vehicle Speed Signal	P0608	P0608	P0608	--

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 malfunction indicator lamp (MIL) will not illuminate.

•	The cruise control system is disabled.

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

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Test drive the vehicle, verify the scan tool Vehicle Speed Sensor parameter is displaying a valid vehicle speed.

⇒	If the parameter does display a valid speed, replace the PCM.

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the TAC module.
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.

If all circuits test normal, replace the TAC module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for PCM or TAC module replacement, setup, and programming