Engine Oil Pressure Indicator Always On 3.6L LY7

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

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

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

⇒	If greater than 1 ohm, test the low reference circuit terminal A 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 terminal B and low reference circuit terminal A.

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

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

4. Verify the scan tool Engine Oil Pressure Sensor parameter is greater than 550 kPa (80 psi).

⇒	If less than 550 kPa (80 psi), test the signal circuit terminal C for a short to ground. If the circuit tests normal replace the ECM.

5. Install a 3-amp fused jumper between the signal circuit terminal C and the low reference circuit terminal A. Verify the scan tool Engine Oil Pressure Sensor parameter is less than 8 kPa (1.2 psi).

⇒	If greater than 8 kPa (1.2 psi), test the signal circuit terminal C for a short to voltage 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, replace the EOP sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Engine Oil Pressure Indicator Always On 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 pressure switch opens, and the PCM should detect a high signal voltage input. The PCM tests the state of the EOP signal circuit with the ignition switch turned ON, and the engine turned OFF. The instrument panel cluster (IPC) illuminates the EOP indicator when the IPC receives a serial data message from the PCM requesting the EOP indicator turned ON.

Schematic Reference

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

Important: Do not turn the key to the crank position or engage the starter at any time during diagnosis.

1. Ignition ON, verify the scan tool Engine Oil Pressure (EOP) Switch parameter is Low.

⇒	If not Low, replace the instrument panel cluster (IPC).

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

⇒	If not OK, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If OK, test or replace the EOP switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.