Engine Oil Pressure Gage Inaccurate or Inoperative 4.2L

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.

Schematic Reference

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

1. Ignition OFF, disconnect 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, perform the engine oil gage sweep test with the scan tool.

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

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Engine Oil Pressure Gage Inaccurate or Inoperative 5.3L

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The engine oil pressure (EOP) sensor changes resistance based on engine oil pressure. The engine control module (ECM) monitors the signal circuit of the EOP sensor. When the oil pressure is high, the sensor resistance is high, and the ECM senses a high signal voltage. When the oil pressure is low, the sensor resistance is low, and the ECM senses a low signal voltage. The ECM sends the engine oil pressure information to the instrument panel cluster (IPC) via the class 2 serial data circuit.

Schematic Reference

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

1. Ignition OFF, disconnect the harness connector at the EOP sensor.
2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.

⇒	If greater than 1 ohm, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.

⇒	If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the ECM.

⇒	If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Install a 3-amp fused jumper wire between the signal circuit and the low reference circuit. Verify the scan tool Engine Oil Pressure Sensor parameter is less than 0.4 volt.

⇒	If greater than 0.4 volt, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. Install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify the scan tool Engine Oil Pressure Sensor parameter is greater than 4.6 volts.

⇒	If less than 4.6 volts, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

6. Ignition ON, perform the engine oil gage sweep test with the scan tool.

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

7. If all circuits test normal, test or replace the EOP sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.