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

The engine oil level switch is a normally closed switch that opens when there is a low engine oil condition. When the switch is open the engine control module (ECM) will detect a high signal voltage input. During a low engine oil condition the ECM sends a high speed GMLAN message to the body control module (BCM). The BCM then sends a message via low speed GMLAN to the instrument panel cluster (IPC) requesting illumination of the CHECK OIL message in the driver information centre (DIC).

Schematic Reference

Connector End View Reference

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Scan Tool Reference

Control Module References

1. Ignition OFF, disconnect the harness connector of the engine oil level switch.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit and ground.

⇒	If greater than 1.0 ohm, test the ground circuit for an open/high resistance.

3. Install a 3-amp fusible link wire between the signal circuit of the engine oil level switch harness and a known ground. Verify the scan tool Engine Oil Level Switch parameter is OK.

⇒	If not OK, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

4. If all circuits test normal, test or replace the engine oil level switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.