Circuit Description
The PCM creates the vehicle speed output signal by pulsing the circuit to ground. The PCM pulses the circuit at the same rate as the vehicle speed signal input. The PCM monitors the voltage on the vehicle speed signal circuit. If the PCM determines that the voltage is out of the normal operating range, a DTC sets.
Conditions for Running the DTC
| • | The engine speed is greater than 400 RPM. |
| • | The ignition voltage is greater than 6 volts but less than 18 volts. |
Conditions for Setting the DTC
| • | The PCM detects that the voltage of the vehicle speed signal circuit is out of the normal operating range. |
| • | The condition must be present for a minimum of 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM stores the DTC information in memory when the diagnostic runs and fails. |
| • | 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. |
Diagnostic Aids
Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics | ||||
1 | Did you perform the Instrument Cluster Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the vehicle speedometer indicate a vehicle speed? | -- | Go to Diagnostic Aids | Go to Step 3 |
3 |
Does the voltage measure greater than the specified value? | 9.5V | Go to Step 5 | Go to Step 4 |
4 | Test the vehicle speed signal circuit of the PCM for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 |
5 | Test the vehicle speed signal circuit of the PCM for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 |
6 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 |
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 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
