Circuit Description
The PCM creates the engine speed signal by pulsing the engine speed signal circuit to ground. The PCM monitors the voltage on the engine 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 and less than 18 volts. |
Conditions for Setting the DTC
| • | The PCM detects that the voltage of the engine speed signal circuit is out of the normal operating range. |
| • | All conditions are present for a minimum of 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM stores the DTC information into 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
Use the Freeze Frame and/or Failure Records data in order to locate an intermittent condition. If the DTC cannot duplicated, the information included in the Freeze Frame and/or Failure Records data can help in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also help in determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions including those for RPM, for engine load, for vehicle speed, for temperature, and for others. This will isolate when the DTC failed.
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 tachometer display the engine RPM? | -- | Go Diagnostic Aids | Go to Step 3 |
3 |
Does the voltage measure greater than the specified value? | 9.0 V | Go to Step 5 | Go to Step 4 |
4 | Test the engine speed signal circuit 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 engine speed signal circuit 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 |
