GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Corvette 🢒 Driver Information and Entertainment 🢒 Displays and Gages 🢒 DTC P0654

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this 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 B0654: Engine Speed Output Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Engine Speed Signal Circuit

P0654

P0654

1

P0654

1. Tachometer Inaccurate or Inoperative

Circuit/System 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 more than 400 RPM.
    • The ignition voltage is between 9-18 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 must be present for a minimum of 5 seconds.

Action Taken When the DTC Sets

The ECM records the operating conditions at the time the diagnostic fails. The ECM displays the failure information in the Failure Records on the scan tool.

Conditions for Clearing the DTC
    • The DTC becomes history when the conditions for setting the DTC are no longer present.
    • The history DTC clears after 40 malfunction-free warm-up cycles.

Reference Information

Schematic Reference

    •  Instrument Cluster Schematics
    •  Engine Controls Schematics for the 6.0L engine
    •  Engine Controls Schematics for the 7.0L engine

Connector End View Reference

    •  Displays and Gages Connector End Views
    •  Engine Control Module Connector End Views for the 6.0L engine
    •  Engine Control Module Connector End Views for the 7.0L engine

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data List

Circuit/System Verification

Start the engine with the scan tool installed. Verify that the tachometer display matches the scan tool Engine Speed parameter in the ECM Engine Data List.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the head-up display (HUD).
  2. Start the engine and verify that the tachometer value does not match the scan tool Engine Speed parameter in the ECM Engine Data List.
    3. ⇒If the tachometer matches the scan tool Engine Speed parameter, test the engine speed signal circuit terminal 4 for a short to voltage, a short to ground or an open/high resistance. If circuit tests normal, replace the HUD.
  3. Ignition OFF, disconnect the C1 harness connector at the engine control module.
  4. Ignition ON, test for 9-11 volts between the engine speed signal circuit terminal 48 and ground.
    5. ⇒If less than 9 volts, test the engine speed signal circuit terminal 48 for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC.
    ⇒If greater than 11 volts, test the engine speed signal circuit terminal 48 for a short to voltage. If the circuit tests normal, replace the IPC.
  5. If all circuits test normal, test or replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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