Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using the diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P0654: Engine Speed Output CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Engine Speed Signal | P0654 | P0654 | P0654 | -- |
1. Tachometer Inaccurate or Inoperative | ||||
Circuit Description
The engine control module (ECM) creates the engine speed signal by pulsing the engine speed signal circuit to ground at a rate of 2 pulses per engine revolution. The IPC converts the 2 pulses per engine revolution signal to a tachometer position indicating the engine speed. The engine speed is sent to the instrument panel cluster (IPC) over a discreet wire from the ECM. The tachometer signal is pulled up to B+ in the IPC. The ECM monitors the voltage at the engine speed signal circuit to determine when the voltage is out of the normal operating range.
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 ECM detects that the commanded state of the driver and the actual state of the signal circuit do not match. |
| • | The above condition exists for a minimum of 5 seconds. |
Action Taken When the DTC Sets
| • | The ECM stores the DTC information in memory when the diagnostic test runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The ECM records the operating conditions at the time when the diagnostic test fails. The ECM stores this information in the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The DTC becomes history when the conditions for setting the DTC are no longer present. |
| • | A history DTC is cleared after 40 consecutive malfunction-free warm-up cycles. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Instrument Cluster Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the X1 harness connector at the ECM. Install a signal generator and instrument panel tester between the engine speed signal circuit terminal 25 and ground:
- Ignition ON, set the signal generator to generate a tachometer signal. Verify that the tachometer indicates a RPM reading.
- If all circuits test normal, test or replace the ECM.
| ⇒ | If no RPM reading is present, test the signal circuit for an open/high resistance, a short to voltage, or a short to ground. If the circuit tests normal, replace the instrument panel cluster (IPC). |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM and IPC replacement, setup, and programming
