Circuit Description
The powertrain control module (PCM) creates the vehicle speed output signal by pulsing the circuit to ground at a rate of 4K PPM. The PCM monitors the voltage at the vehicle speed output circuit. If the PCM determines that the voltage is out of normal operating range, the PCM sets a DTC.
Conditions for Running the DTC
| • | The engine speed is more than 400 RPM. |
| • | The ignition voltage is between 9.0 volts and 18.0 volts. |
Conditions for Setting the DTC
| • | The PCM detects that the commanded state of the driver and the actual state of the signal circuit do not match. |
| • | The condition above must be present for a minimum of 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM stores a DTC P0608 in memory when the diagnostic test runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM records the operating conditions at the time the diagnostic fails. 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. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems | ||||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the voltage measure greater than the specified value? | 9.0 V | Go to Step 3 | Go to Step 4 |
3 | Test the vehicle speed signal circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 5 |
4 | Test the vehicle speed signal circuit for an open or for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 6 |
5 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
6 | Inspect for poor connection at the harness connector of the instrument panel cluster (IPC). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
7 |
Important: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 8.1L.Did you complete the replacement? | -- | Go to Step 9 | -- |
8 |
Important: Program the replacement IPC. Replace the IPC. Refer to Instrument Cluster Replacement .Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
