Circuit Description

Engine oil pressure switch is a normally closed switch. When oil pressure increases to greater than 1 or 4.5 psi, switch contact opens. PCM supplies 12 volts to oil pressure input circuit. When oil pressure is low, the 12 volts is pulled low to ground. This test checks for a short to ground in the low oil pressure switch circuit. If engine has been off long enough for engine temperature to drop by 10°C, then an open (low oil pressure) condition of the circuit should be observed prior to engine start. If engine has not been cranked and low oil pressure has not been detected, DTC P1189 will set. DTC will also set if circuit is shorted for 5 seconds.