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 engine control module (ECM) should detect a low signal voltage input. With the engine running, the pressure switch opens, and the ECM should detect a high signal voltage input. The ECM tests the state of the EOP circuit with the ignition switch turned ON, and the engine turned OFF. When the oil pressure is low, the ECM sends a GMLAN serial data message to the body control module (BCM) requesting the EOP indicator turned ON. The instrument panel cluster (IPC) illuminates the EOP indicator when the IPC receives a serial data message from the BCM 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 of the EOP switch for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If OK, replace the EOP switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.