Engine Oil Pressure Gage Inaccurate or Inoperative

Engine Oil Pressure Gage Inaccurate or Inoperative (4.2L)

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.

Circuit Description

With low oil pressure, the engine oil pressure (EOP) switch closes, and the signal circuit is low. With oil pressure above 4.5 psi, the EOP switch opens, and the signal circuit is high. The powertrain control module (PCM) monitors the oil pressure switch signal circuit, and sends a class 2 message to the instrument panel cluster (IPC), indicating the switch status.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the EOP switch.
2. Ignition ON, verify the scan tool Engine Oil Pressure Switch parameter is OK.

^ If not OK, test the signal circuit of the EOP switch for a short to ground. If the circuit tests normal replace the PCM.

3. Ignition ON, with a scan tool perform the IPC Gauges test. The oil pressure gauge should sweep from high to low.

^ If the engine oil pressure gauge does not sweep from its low to high position, replace the IPC.

4. If all circuits test normal, test or replace the EOP switch.

Repair Instructions

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

* Engine Oil Pressure Sensor and/or Switch Replacement