Oil Pressure Gauge
WARNING: This page is about a different car, the 2005 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The instrument cluster is hardwired to the oil pressure switch. The oil pressure switch consists of a diaphragm and contact points, which are normally open. When there is low or no oil pressure, the oil pressure switch remains open and removes the ground to the instrument cluster. When sufficient oil pressure exists, the oil pressure switch closes, providing a ground signal to the instrument cluster. The instrument cluster monitors the oil pressure and provides the oil pressure gauge indication with a corresponding pointer movement.