P0654

DTC P0654

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using the diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptor
DTC P0654
- Engine Speed Output Circuit

Diagnostic Fault Information





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

Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Instrument Cluster Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. 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:
2. Ignition ON, set the signal generator to generate a tachometer signal. Verify that the tachometer indicates a RPM reading.

• 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).

3. If all circuits test normal, test or replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

Control Module References (Programming and Relearning) for the ECM and IPC replacement, setup, and programming