Engine Oil Pressure Indicator Malfunction 3.8L L26 and L32

The engine oil pressure (EOP) switch is a normally closed switch that opens with the proper oil pressure. With the ignition switch turned ON and the engine not running, the powertrain control module (PCM) should detect a low signal voltage input. With the engine running, the oil pressure switch opens and the PCM detects a high signal voltage input. When the oil pressure is low, the PCM sends a serial data message to the instrument panel cluster (IPC) requesting the EOP indicator turned ON. The IPC illuminates the EOP indicator when the IPC receives a serial data message from the PCM requesting the EOP indicator turned ON.

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, engine running, verify the scan tool Engine Oil Pressure Switch parameter is OK.

1. Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) switch.
2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the PCM.

3. Ignition ON, verify the scan tool Engine Oil Pressure Switch parameter is OK.

⇒	If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the PCM.

4. Ignition ON, install a 3A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool Engine Oil Pressure Switch parameter is Low.

⇒	If not the specified value, test the signal circuit for an open/high resistance. If circuit test normal, replace the PCM.

5. If all circuits test normal, test or replace the engine oil pressure switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Engine Oil Pressure Indicator Malfunction All Other Engines

The engine oil pressure (EOP) sensor changes voltage based on the engine oil pressure. The EOP sensor is a 3-wire sensor comprising of the signal circuit, the low reference circuit and the 5-volt reference circuit. The engine control module (ECM) supplies 5 volts to the EOP sensor via the 5-volt reference circuit and provides ground via the EOP low reference circuit. The ECM monitors the signal circuit of the EOP sensor to determine the EOP sensor voltage is within the normal operating range of approximately 1-4 volts. When the engine oil pressure is high, the EOP sensor voltage is high and the ECM senses a high signal voltage. When the engine oil pressure is low, the EOP sensor voltage is low and the ECM senses a low signal voltage. The ECM sends the EOP data via the serial data circuit to the instrument panel cluster (IPC).

Schematic Reference

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, observe the scan tool Engine Oil Pressure Sensor parameter. The reading should be between 41-448 kPa (6-65 psi).
2. Verify the engine oil pressure, refer to Oil Pressure Diagnosis and Testing for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engine.

1. Ignition OFF, disconnect the harness connector at the engine oil pressure (EOP) sensor.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal A and ground.

⇒	If greater than the specified range, test the low reference circuit for 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 terminal B and ground.

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

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

4. Verify the scan tool Engine Oil Pressure Sensor parameter is less than 8 kPa (1.2 psi).

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

5. Install a 3A fused jumper wire between the signal circuit terminal C and the 5-volt reference circuit terminal B. Verify the scan tool Engine Oil Pressure Sensor parameter is greater than 550 kPa (80 psi).

⇒	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 ECM.

6. Ignition ON, command the indicators OFF with the scan tool.

⇒	If the EOP indicator does not turn OFF, 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.