Low Engine Oil Pressure Indicator Diagnosis

CIRCUIT DESCRIPTION
The engine oil pressure switch is normally closed. When engine oil pressure increases above 1 to 4.5 psi the switch contacts open. The PCM supplies 12 volts to the oil pressure input circuit. With low oil pressure the 12 volts is pulled low to ground. When the PCM monitors a low oil pressure condition the PCM will command a message be displayed on the Driver Information Center (DIC) or Instrument Panel Cluster (IPC) depending upon vehicle model. The PCM will also increase the Desired Idle engine speed in an attempt to raise engine oil pressure.

MESSAGE CONDITIONS
^ Engine speed is more than 57 RPM for 4 seconds.
^ The engine oil pressure switch indicates low oil pressure for 4.2 seconds.

The Message is cleared when the engine oil pressure switch indicates oil pressure or when engine speed is 0 RPM.

IDLE SPEED INCREASE CONDITIONS
^ Engine speed is more than 400 RPM for 3 seconds.
^ The engine oil pressure switch indicates low oil pressure for 3 seconds.

The Desired Idle speed is commanded to a minimum engine speed of 744 RPM.

Desired Idle is returned to normal PCM control when the engine oil pressure switch indicates oil pressure or when engine speed is 0 RPM.

TEST DESCRIPTION
4. If the Oil Pressure parameter indicates OK when disconnected measure the engine oil pressure with a mechanical gauge. Refer to Engine Mechanical. Ensure that engine oil pressure is within operating specifications before replacing the Engine Oil Pressure Switch.
6. If the fuse in the jumper opens when probing the circuit repair the short to voltage on the oil pressure input circuit.