The oil pressure sensor, often referred to as the oil pressure sender, is a unit responsible for telling a vehicle's computer the oil pressure. It controls the gauge on a vehicle, which lights up as a warning indicator. This signals that the automobile's engine is receiving too little oil pressure or the sending unit is faulty. Low oil pressure could mean that not enough oil is present and can be easily fixed with additional oil. It might also indicate that the engine is burning oil or that an oil leak exists. If the sensor, or sending unit as some call it, is to blame, it can be easily tested.
Insert the key into the ignition, and turn the key to the accessory setting. The engine should not be running.
Look at the oil gauge on the dashboard. Unplug the wire that is connected to the sending unit, if the gauge is at zero. If the gauge goes up to three, it indicates that the sender is bad and needs to be replaced.
Hold the end of the unplugged wire from the sending unit, and touch it to the negative part of the battery or to any other metal piece in the vehicle. If it shows zero on the oil gauge, it is a good sender and is not faulty.
The sender could be bad if the oil gauge is reading full pressure when the vehicle is not on.