Circuit/System Description
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
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 ENGINE OIL LOW ADD OIL message in the driver information center (DIC).