Oil pressure sensor: how it works, problems, testing

An oil pressure sensor (switch) is a vital component of any car engine. It monitors the oil pressure in the lubrication system. How it works:

The engine lubrication system supplies oil under pressure to all rotating and moving parts inside the engine. An oil pump draws the oil from the oil pan, and pumps it through the oil filter and into the lubrication system channels. Through the channels, the oil is delivered under pressure to main and other bearings, camshafts and other rotating and moving parts of the engine. Without oil pressure any engine won't last more than a few minutes.

An oil pressure sensor (switch) is usually installed in the cylinder block close to an oil filter or at the oil filter housing. There are two types of oil pressure sensors: In most cars, an oil pressure sensor is a simple switch that opens the electrical circuit when there is minimum required oil pressure. In other cars, an oil pressure sensor measures the actual oil pressure. How a simple switch-type oil sensor works: When the ignition is turned on, but the engine is not running, there is no oil pressure and the switch is closed. The low oil pressure warning light is illuminated. When the engine is started, the oil pump starts working building the oil pressure. When the minimum required pressure is reached, the oil pressure switch opens and the warning light on the dash turns off.

Oil pressure sensor problems

One of the common problems is when the oil pressure sensor (switch) starts leaking oil. The oil could leak from the sensor itself or from the tread. If the oil leaks from the tread, your mechanic may recommend resealing it. If the sensor itself is leaking, it will have to be replaced.

Another common problem with the oil pressure sensor is when it clogs up or fails inside and cannot read the oil pressure correctly. That can cause the low oil pressure warning light to come on even when there is enough pressure.

In some cars a failed oil pressure sensor can cause the Check Engine light to come on with the code P0520 - Engine Oil Pressure Sensor Circuit. For example, it's a common problem in many Dodge/Chrysler/Jeep cars. When the code P0520 is present the first step is to check for service bulletins. For example, the Chrysler service bulletin 18-034-14 REV. A recommends replacing a failed oil pressure sensor with a revised part if the fault is confirmed. If there is no bulletins, the sensor electric circuit (wiring, connectors) must be checked too.

How the oil pressure sensor is tested

The testing procedure is different depending on the type of the sensor. The first step is usually to verify the engine oil level and condition, because often the low oil pressure warning light comes on because of the low oil level.

A typical testing procedure require a technician to check the wiring to the sensor and test the actual oil pressure of the engine lubrications system. To measure the oil pressure, mechanics use an oil pressure gauge that connects in place of the oil pressure sensor with a special adaptor. If the oil pressure is very low when the engine is running, it's an internal engine problem. If the pressure is within specs, and the sensor wiring checks out OK, the sensor is bad and must be replaced.

Because the oil pressure test takes considerable amount of time and the oil pressure sensor is not very expensive, your mechanic may advise replacing the sensor first and see if it fixes the problem. We know of many cases where the new oil pressure sensor solved the problem with the oil pressure light coming on.

If the sensor and its wiring are good and the oil is at the proper level, but the oil light still comes on with the engine running, it might be internal engine problem or an issue with the lubrication system, such as a bad oil filter or clogged up oil pickup screen. In this case, further diagnostics will be required.

Oil pressure sensor replacement

Depending on the location, replacing the oil pressure sensor may cost from 0.5 to 1.8 hours of labor plus the part.