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Signs You Have a Bad Oil Pressure Sensor

By Mia Bevacqua, May 14, 2018

A loss of oil pressure can quickly result in engine failure — that’s very bad news. The oil pressure sensor, known as either a switch or sender, aims to prevent this dire situation. Let's learn more about this sensor, or you can jump ahead to signs of a failing one, or get some repair advice.

If there’s a dark staircase in your house, you might install an automatic light so you can safely proceed when you need to climb it. The oil pressure switch and light on your car serve a similar purpose. When you turn on the ignition key to the “run” position, you should have a red light on the dash. The oil pressure switch is testing the bulb for you. When you start the engine, the switch will turn off the red light almost immediately. If the light stays on, or comes on while you drive, you know you’ll have to shut it off and find out why. 

Get it diagnosed by a professional
 

What the oil pressure sensor does

The oil pressure switch or oil pressure sender is designed to warn the driver when the oil pressure gets too low. Exactly how oil pressure is measured depends on whether the vehicle is equipped with an oil pressure gauge or a warning light.

Oil pressure gauge: Vehicles with an oil pressure gauge use an oil pressure sender. This device changes its internal resistance as the oil pressure fluctuates. The signal from the sender is then sent through wires to oil pressure gauge on the dash, where it causes the needle to move. 

Oil pressure warning light: Vehicles with a warning light use an oil pressure switch. The switch may be either normally open or normally closed. When the oil pressure gets too low, the switch will change to the other position to turn on the warning light.  

The signal from the oil pressure switch or sender may be sent directly to the instrument cluster, or it may be first sent to the engine control unit (ECU) — in essence, the engine’s computer. In this latter case, the ECU will share the oil pressure information with the instrument cluster. In response, the cluster will either move the gauge or turn on the warning light, if needed.

It’s also worth noting that the oil warning light bulb is part of the electrical circuit for the oil pressure. In other words, a bad bulb can cost you your engine because it can’t warn you when you have no oil pressure. 

If the red oil pressure warning light comes on while you’re driving, or your gauge plummets, pull over to the side of the road when it is safe and shut the vehicle off until the cause of failure is determined. This may mean you need to have your car towed to a repair shop.

Signs of a failing oil pressure switch

A faulty oil pressure switch or sender can cause several problems. Because of the dangers associated with low oil pressure, it’s important to get these checked out right away if you experience them.

Your check engine light is on: In many cases, the ECU monitors the operation of the oil pressure sensor. If it detects a problem, it will turn on the check engine light

Oil pressure gauge or warning light malfunctions: Depending on how the device fails, a faulty oil pressure switch may cause the oil pressure warning light to be on all the time, or not function at all. A failed sender may cause the gauge to be pegged at high, or not function at all. It may also cause inaccurate or intermittent gauge operation.   

Oil leaks: A bad oil pressure switch or sender may leak engine oil. Oil leaks can be caused by a number of issues, so a professional inspection is order here.

» MORE: Get an estimate for your oil pressure sensor replacement

How to fix the problem

It’s important to be able to monitor your oil pressure at all times. But before spending time and money to replace the oil pressure sensor, a thorough diagnosis should be performed. A professional mechanic can do this using equipment such as a scan tool, digital multimeter and mechanical oil pressure gauge. 

If you suspect you have low oil pressure, it’s a good idea to check your oil level. You can find more information on how to do this here, but in general, you’ll want to pull your engine’s dipstick and make sure it’s registering somewhere between “low” and “full.” If it’s too low, you should add more oil before driving.

A faulty oil pressure switch or sender should be replaced immediately. On some vehicles, the switch or sender is simple to access and replacement is easy — here’s how to do it. But on others, it’s buried deep within the engine compartment, requiring significant disassembly of various parts and making it a job best left to a professional.

 

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