DTC P0654. GMC Truck TopKick C-Series (Conventional) C4/C5 2008

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Driver Information and Entertainment 🢒 Displays and Gages 🢒 DTC P0654

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 Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Engine Speed Signal	B0560, P0654	B0560, P0654	B0560, P0654	--

The engine control module (ECM)/powertrain control module (PCM) creates the engine speed signal by pulsing the signal circuit to ground at the rate of 2 pulses per engine revolution. The ECM/PCM monitors the voltage at the engine speed signal circuit. If the ECM/PCM determines that the voltage is not within the normal operating range, the ECM/PCM sets a DTC.

Conditions for Running the DTC

•	The engine speed is greater than 800 RPM.

•	The ignition voltage is greater than 9 volts but less than 18 volts.

Conditions for Setting the DTC

•	The ECM/PCM detects that the commanded state of the driver and the actual state of the signal circuit do not match.

•	The above condition is present for at least 5.0 seconds.

Action Taken When the DTC Sets

•	The ECM/PCM stores a DTC P0654 in memory when the diagnostic runs and fails.

•	The malfunction indicator lamp (MIL) will not illuminate.

•	The ECM/PCM records the operating conditions at the time when the diagnostic test fails. The ECM/PCM stores this information in the Failure Records.

Conditions for Clearing the DTC

•	A 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.

Reference Information

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

Ignition OFF, disconnect the harness connector at the ECM/PCM. Install a signal generator and instrument panel tester between ground and the following engine speed signal circuit:

•	Terminal 28 (LF8)

•	Terminal 38 LF6)

•	Terminal 10 (L18)

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).

If all circuits test normal, test or replace the ECM/PCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the ECM/PCM and IPC replacement, setup, and programming