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. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
Engine Speed Signal Circuit | P0654 | P0654 | P0654 |
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 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.
Reference Information
Schematic Reference
| • | Engine Controls Schematics for the 4.6L engine |
| • | Engine Controls Schematics for the 4.4L engine |
Connector End View Reference
| • | Engine Control Module Connector End Views for the 4.6L engine |
| • | Engine Control Module Connector End Views for the 4.4L engine |
Description and Operation
Instrument Cluster Description and Operation
Electrical Information Reference
Scan Tool Reference
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
- Ignition ON, with the scan tool installed, perform the IPC Gage Sweep Test in the IPC Output Controls. Verify the tachometer dial moves from the minimum to the maximum position and back to the tachometer minimum position.
- Ignition OFF, disconnect the C1 harness connector at the engine control module.
- Ignition ON, test for 9-11 volts between the engine speed signal circuit terminal 25 and ground.
- If all circuits test normal, test or replace the ECM.
| ⇒ | If the tachometer does not perform the IPC Gage Sweep Test, replace the IPC. |
| ⇒ | If less than 9 volts, test the engine speed signal circuit 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 for a short to voltage. If the circuit tests normal, replace the IPC. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM or IPC replacement, setup and programming
