• | 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. |
Circuit | Short to Ground | High Resistance | Open | Short to Voltage |
---|---|---|---|---|
Engine Speed Signal | P0654 | 1 | P0654 | P0654 |
1. Tachometer Inaccurate or Inoperative |
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 instrument panel cluster (IPC). The ECM monitors the voltage at the engine speed signal circuit to determine when the voltage is out of the normal operating range.
Instrument Cluster Description and Operation
Control Module References for scan tool information
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.
⇒ | If the tachometer does not perform the IPC Gage Sweep Test, replace the IPC. |
⇒ | 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 the circuit tests normal, replace the HUD. |
⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the IPC. |
⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the IPC. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM, IPC and HUD replacement, setup and programming