Engine Oil Pressure Switch

The engine oil pressure switch is a normally open switch with no oil pressure and is hardwired to the PCM  . The PCM  provides a reference voltage to the engine oil pressure switch. When the oil pressure is within normal limits, the engine oil pressure switch closes to ground pulling the reference voltage low to the PCM  . When the oil pressure is low, the engine oil pressure switch is open sending the reference voltage high to the PCM  .