Oil Pressure Gauge
WARNING: This page is about a different car, the 2004 Mercury Mountaineer and 2004 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
The instrument cluster is hardwired to the engine oil pressure switch. The engine oil pressure switch consists of a diaphragm and contact points, which are normally open. When there is low or no oil pressure, the engine oil pressure switch remains open and removes the ground to the instrument cluster and when sufficient oil pressure exists, the engine oil pressure switch closes providing a ground signal to the instrument cluster. The instrument cluster monitors the oil pressure and commands the oil pressure gauge indication with a corresponding pointer movement.