How To Tell If Oil Pressure Sensor Is Bad?

how to tell if oil pressure sensor is bad

You’re wondering how to tell if oil pressure sensor is bad? Depending on your car model or year, it’s good to know from the beginning which kind of sensor you have. If it’s a simple switch, then things can be easier to perform. In case of an oil pressure sensor which is sending a variable reading proportional to pressure, it means that your car is newer and more electronic units are processing the signal. But let’s dive in.

Check your oil dipstick and see what is the oil level. If the oil level is within limits, meaning is somewhere in the middle of the low and high bars, then it means that oil pressure sensor might be the culprit. It’s very important not to drive your car if the oil pressure light is turned ON, unless you know for sure that is the oil pressure sensor.

What is the oil pressure sensor?

Oil is very important for your engine’s life. It’s lubricating all the moving parts and prevents early wear because of movement. However, is the same important to have a good pressure in this lubricating system.

Oil is displaced by oil pump, through all the engine’s galleries and all the bearings. In this process, the walls of the cylinders are also lubricated by intermittent jets.

The oil pressure is dependent on the moment in time of your engine. In the startup, the pressure is high because of the viscosity of the oil and as the engine is getting hotter the pressure is lowering.

The oil pressure sensor or switch is a small device that is signaling when the oil pressure inside the system is not within the right parameters. It is usually placed on the engine block based on a threaded system. The end of the sensor is inserted into the connector that’s coming from the engine’s harness.

When the sensor is detecting a pressure that is too low, it sends a signal to the engine control unit which will highlight the issue in the car’s dashboard.

How does an oil pressure sensor works?

By knowing the working principle, then it’s more easy to learn how to tell if your oil pressure sensor is bad. The device is not very complicated, and it’s based on a mechanical movement.

Usually, depending on the sensor, it can have a normally closed or normally opened contact. When the pressure is too low, the spring inside the sensor will be moved.

This movement will either close or open an electrical circuit. When this circuit is closed, a signal will be sent to the electronic unit which will trigger an event for an issue with the pressure inside the system.

I will leave you a picture below with a pressure switch. This is mostly used in older cars:

how a oil pressure switch works

Here, when the oil under pressure is entering the sensor/switch, the spring is tensioned and then the two contacts are touching each other. This way the electrical circuit is closed through the metal plate and it defines a signal.

By always having a constant oil pressure, the electrical circuit is regularly closed. When the pressure is going under the normal value, the spring is not tensioned. Then the two contacts are not touching anymore, thus it opens the circuit. This change of signal is then processed, and will interpreted in a warning.

This warning is telling you that somewhere you have a problem or in most cases a bad oil pressure sensor.

On newer cars, the oil pressure sensor is using 3 wires like the one in the picture below. Here the output signal is based on a variation in voltage. The sensor is energized by a power supply and on a third wire it returns a voltage proportional to the oil pressure.

3 wires oil pressure sensor

Can you drive with a bad oil pressure sensor?

Here is a good question, but the issue is figuring out if the oil pressure sensor is actually the culprit. If the low pressure light is turned on in your cluster, it’s wise to turn off the engine as soon as possible.

Having a good oil pressure inside the system is very important for the good functioning of the engine. You never know if the pump is failing or the oil filter is clogged. But in our case we want to check how to tell if oil pressure sensor is bad.

The oil pressure sensor is sending a warning that the pressure is not correct, but in case everything is working fine, then the only inconvenient will be the light on your dashboard.

First, check the oil level using the dipstick to check if the oil pressure is too low. If the mark is between low and high interval, then it’s fine. Then try to listen to the motor. If you hear that is grinding, or the noise is unusual might be a problem.

If the sound is smooth and like it was before, then it’s a good sign.

In conclusion, if you feel that the engine it’s not sounding noisy and the oil level is correct, you can drive like that. However, if you hear strange noises, pull over and stop the engine.

Maybe the oil pressure sensor or other components that send the signal are faulty and are causing a wrong signal, which is incorrect.

How to test oil pressure sensor or switch

Now it depends if you have only a normal switch sensor or a more complex sensor, which is sending the signal based on the oil applied pressure. For a normal oil switch sensor we can use the picture below. We will need a multimeter to perform this test.

how to test a oil pressure switch

Place the multimeter on (Ohm) or Diode (beep). Next we will place the multimeter probes, one on the sensor’s thread and the other on the connector part of the sensor. Depending on the switch type you will see a resistance value or hear a beep when the switch is normally closed. If it’s normally opened, you will have a value when you apply some pressure on the sensor entrance.

If we have a more complex oil pressure sensor/sender, like in the picture below, it’s more complex:

how to test a oil pressure sensor-sending unit

First, we will need a power supply for the sensor itself. If you don’t have a 5V power supply, try to check the sensor specifications if more than 5V can power it.

Once you do that, you need to apply a pressure in the sensor. You can try to use some compressed air, which is simulating the oil that’s entering.

Then you will need to set the multimeter on V – DC (direct current) and set the probes accordingly. After measure between the 0V (ground) and the sensor output pin. You should have a voltage proportional to the pressure you are applying.

Remember that we are just testing now the functionality, not if the values are correct. Maybe even we have signal the variable resistance inside the sensor to be faulty.

Probably the best answer will provide a diagnosis on the vehicle. Then you can get for sure if the values match the specifications.

How much does it cost to replace the sensor?

The sensor itself, it’s not very expensive, depending of course if it’s a switch or a sensor. The price varies between $20 to $160 depending on your car model year and other factors. For the labour you can expect anywhere between $60 to $200 again depending on the service or mechanic that’s performing the action.

You can also do it yourself if you know for sure we’re dealing with a faulty oil pressure sensor. The threaded system makes it easy to dismount and place the new one. Most of the times, you can struggle in accessing it.


We’ve put in some small topics ways how to know if your oil pressure sensor is bad. Remember that if only the sensor is the issue then you don’t need to worry too much. However, if other components are responsible, like the oil pump or clogged transporting system, then it’s good to get some professional advice from a mechanic or a car service.


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