Diagnostic Instructions
DTC Descriptor
DTC P0608 00: Vehicle Speed Output Circuit
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 universal asynchronous receiver transmitter (UART) 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 vehicle speed sensor (VSS) DTCs present in the PCM. |
| • | 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 UART serial data message to the PCM indicating that the vehicle speed is 0 km/h (0 mph). |
| • | The condition must be present for greater than 4 seconds. |
Action Taken When the DTC Sets
| • | The cruise control system is disabled. |
| • | The PCM stores a DTC P0608 in memory. |
| • | The PCM records the operating conditions at the time the DTC sets. The PCM displays the failure information in the Failure Records on the scan tool. |
Conditions for Clearing the 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 PCM receives the clear code command from the scan tool. |
Diagnostic Aids
Reference Information
Schematic Reference
Instrument Cluster Schematics
Connector End View Reference
Electrical Information Reference
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Verification
- Ignition OFF, install a scan tool and raise the vehicle drive wheels. Refer to
Lifting and Jacking the Vehicle
.
- Engine ON, transmission in Drive, verify the scan tool Vehicle Speed Sensor parameter reads any vehicle speed.
| ⇒ | If the scan tool parameter does not read any vehicle speed, go to Diagnostic Aids if DTC P0502 or P0503 are current in the PCM. If those codes are not current, replace the PCM. |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the TAC module.
- Ignition ON, test for 8.5 volts between the vehicle speed signal terminal 4 and ground.
| ⇒ | If less than the specified value, test the vehicle speed signal circuit for a short to ground. If the circuit tests normal, replace the PCM. |
| ⇒ | If greater than the specified value, test the vehicle speed signal circuit for a short to voltage. If the circuit tests normal, replace the TAC module. |
- If all circuits test normal, replace the PCM.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for PCM or TAC module replacement, setup, and programming
