Circuit Description
The PCM creates the vehicle speed signal by pulsing the circuit to ground. 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 commanded state of the driver and the actual state of the signal circuit do not match. |
| • | 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
| • | 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 . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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 the correct speed? | -- | Go to Diagnostic Aids | Go to Step 3 |
Measure the voltage from the vehicle speed signal circuit to a good ground. Does the voltage measure greater than the specified value? | 9.5V | Go to Step 4 | Go to Step 6 | |
4 | 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 8 | Go to Step 5 |
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 8 | Go to Step 7 |
6 | Repair the short to ground in the vehicle speed signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | 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 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
