Engine Oil Pressure Switch
WARNING: This page is about a different car, the 2019 Ford SSV Plug-in Hybrid, 2019 Ford Police Responder Hybrid, and 2019 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
Without oil pressure, the engine oil pressure switch is a normally closed switch. The PCM provides a reference voltage to the engine oil pressure switch when the ignition is in RUN. With the engine running and low or no oil pressure, the engine oil pressure switch closes. The PCM detects the reference voltage pulled low to ground and provides a request to the IPC to illuminate the low oil pressure warning indicator. With the engine running and sufficient oil pressure, the engine oil pressure switch opens, sending the reference voltage high. The PCM detects the high reference voltage and provides a request to the IPC to turn off the low oil pressure warning indicator.