How Does an Oil Pressure Sensor Work

An oil pressure sensor is an integral part of an engine, responsible for monitoring the internal pressure. It functions on the principle that whenever the pressure deviates from a given range, detection and indication are done by the sensor and the switch.

Ensuring appropriate oil leads to maintaining a robust and high-performing engine. Apart from fuel, oil also functions as a lubricant and regulates engine temperature and cooling.

The oil pump is the tool for providing the pressurized engine oil to various parts. This helps you avoid costly engine repairs and sudden breakdowns.

Essentially, an oil pressure sensor consists of two critical components: a spring-loaded switch and a diaphragm. The Oil pressure switch and oil pressure sensor are not identical. The oil pressure switch vs. sensor puzzle can be solved by understanding their respective functions.

An oil pressure sensor is tasked with detecting changes in pressure in the engine. However, an oil pressure switch is responsible for turning on the indicator on the dashboard in case of oil pressure fluctuations.

The switch is a device that opens or closes a set of contacts or circuits to reflect abnormal deviations in oil pressure. Both the sensor and switch function in tandem to let the driver know if the pressure has crossed the set range.

How Does Oil Pressure Sensor Work:

How does it lead to switching on the indicator on the dashboard? It operates on the simple principle of converting pressure into an electrical signal, displayed by the analog gauge or light indicator.


The diaphragm is made of a thin aluminum oxide membrane. The diaphragm-switch assembly is usually fixed in one of the oil passageways. The objective is to expose the diaphragm directly to the oil pressure to get the most accurate readings.

The resistance of the diaphragm depends upon the oil pressure. Oil flows into the end of the sensor and exerts a push against the diaphragm. After the oil applies the pressure, the reading process of the sensor depends upon the switch mechanism.

Some vehicles have a gauge to reflect the pressure reading, while others have an indicator/warning light to flag abnormal rise or drop. The process of functioning also varies.


In order to make the gauge operational, electric current is supplied through a wire-wound coil, around or within the gauge's needle's pivot. This generates a magnetic field, which facilitates the movement of the needle across the enumerated meter.

The reading which it would give is proportional to the amount of current flowing through the gauge. This is directly affected by the resistance of the gauge's return wire connected to the sensor.

Now, the pressure applied on the diaphragm by the oil causes the movement of a wiper inside the sensor. This wiper is the bridge between the sensor and the return wire of the gauge.

The higher the pressure, the more is the movement of the diaphragm. Consequently, more movement of the wiper and the resultant reading of the needle in the gauge.

Light Indicator

If the dashboard is equipped with the indicator mechanism, the functioning changes slightly. The function of the diaphragm remains the same.

However, the dynamics of the switch and the process of indication change. There is a spring-loaded switch in this case. The oil pressure's force on the diaphragm is substantial to overcome the spring. This keeps the switch in an open circuit as long as the pressure is in the set range.

In case the oil pressure falls below the set limit, the spring force is more. Thereby resulting in a closed circuit and the warning light/lamp is lit.

An electrical current passes from a fuse to the oil pressure switch at the time of switching on the engine. This ensures the warning indicator is 'off' and is the reason behind the initial lighting of the indicator when the engine is switched on.


Generally, in both cases, the effects of surrounding temperature are balanced off with other modifications to the sensor-switch assembly. This gives precise readings. 

Some vehicles are not equipped with a high oil pressure indicator. It is also important to note that the process behind the indication varies from model to model.

Symptoms of a Bad Oil pressure Sensor or Switch

An oil pressure sensor and switch assembly are built to last as long as the car. However, due to multiple reasons, the sensor may begin to function incorrectly, leading to misleading readings/indications. It would be best if you watched out for these signs:

Erratic Blinking of the Oil Pressure Indicator

If the indicator lights up suddenly or begins to blink. This could mean low oil pressure, but it is not necessary all the time.

If your oil level is good and the engine sound is smooth without rough idling, this would mean a faulty oil pressure sensor. It is best to inspect the sensor to avoid any damage to the engine.

Check Engine or Oil Light

Some vehicles do not have a dedicated oil pressure indicator but a 'Check Engine' light. This need not necessarily mean low oil pressure or faulty sensor.

However, it is always safer to get the sensor checked. The flashing of the oil light is considered the surest sign of a defective sensor.

Wrong Readings on Oil Pressure Gauge

If the oil pressure gauge reads zero or very high during running, this could be a faulty sensor. In either case, make sure to check the dipstick. If the oil levels are substantial and no weird engine noise, then the erroneous readings could be due to other reasons.

A very high reading may be due to an internal short in the sensor. If the signal pathway has been heavily damaged, you get a zero reading.

A corroded plug or damage to the wiring harness and even an unplugged connection can give faulty readings. It is best to check other aspects as well before concluding.

Faulty oil pressure sensors can be lethal to the engine. If you are not alerted about the low pressure, it can cause irreparable damage to the engine. This would lead to engine replacement along with exorbitant repair costs.

How do I fix my oil pressure sensor

There is no practical way to fix faulty oil pressure sensors as they are complex encased mechanical units. The rationale is to replace the oil pressure sensor. You can do it by availing of the services of a professional mechanic or even by yourself.

The former is preferable to avoid any further damage. If you choose to replace it yourself, then do adhere to the following:

  1. Locate the oil pressure sensor switch assembly and unplug the electrical connector.
  2. Loosen and remove the sensor with the appropriate wrench/socket.
  3. Compare the new and old pressure sensors. Please make sure they are of the same attributes.
  4. Fit the new sensor properly.
  5. Re-connect the electrical connector
  6. Start the engine to check if the new sensor functions properly.


1. Where is the oil pressure sensor?

The sensor is generally fixed in the engine blocks or cylinder heads. However, there exists no industry standard. Thus, its location varies from model to model and company to company. Consulting the manual is essential.

2. Will my car run without an oil pressure sensor?

Technically, no. The oil pressure sensor forms an integral part under the hood. It indicates the oil pressure. If the same information is not relayed to the driver, it can cause grave problems.

The low oil pressure would damage the engine and make it susceptible to bursts or shorts. In some models, the absence of the sensor would lead to the non-starting of the car as the computer would not permit it.

3. Does oil pressure switch affect fuel pump?

It depends upon the build of your car. A faulty switch may cause the fuel pump not to prime up. In other cases, it may not affect the pump at all.

4. Can a bad oil pressure sensor causing overheating?

Indirectly, yes. If the sensor is faulty, there are incorrect readings/indications on the dashboard. The actual low oil pressure due to insufficient oil in the engine can cause excessive friction. Thereby leading to overheating.


The oil pressure sensor and attached switch assembly are crucial for long-term engine and car performance. Now that you know the functioning, symptoms, and related tips, there should be no delay in maintaining the pressure sensor.

The slightest oversight of any kind can eventually wreck your engine. This would also lead to very high costs and reduced quality of functioning of the vehicle. Proper readings of the oil pressure would prompt you to take remedial steps at the correct time.

The continuous technological improvements would allow for better and robust oil sensors to last longer, despite wear and tear. The synchronous functioning of the oil pressure switch is paramount and is the other essential half of the pressure sensor.

No shortcomings in the switch's operation should be overlooked as a mere mishap. After all, everything is good under the hood, ensuring a smooth experience and meeting all your expectations regarding your vehicle.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top