Most people who own a car know the feeling: It’s a beautiful day outside, you’re cruising down the highway with the window rolled down–and then a chill comes over you as one of the warning lights on the dashboard suddenly illuminates. This time, just as you touch your brake to slow down for a stop sign, the oil light starts to flash orange.

Why does the oil light come on when braking? While there is no way to know for certain why the oil light in your car comes on when braking without doing a thorough inspection of your vehicle, it is most likely being triggered by one of three scenarios:

A faulty oil pressure sensor
A bad oil pump
A leak somewhere in the engine

Even though the severity of these issues varies and may not indicate any imminent danger to your vehicle, an illuminated oil light is not something to be ignored. It is best to keep your vehicle off the road while the oil light is on until you discover the cause. Most auto parts stores can do a quick diagnostic test on your vehicle and let you know the severity of the issue.

Why Oil Light Comes on When Braking

The oil pressure light is located on the dashboard and is typically in the shape of an oil can. If not, some vehicles may simply flash a warning saying, “check oil level.” There are a great many reasons your oil light may come on when braking, with some being quite evasive to pinpoint.

The first place to start is to check and make sure that you are not overdue for an oil change. Degraded oil can sometimes lose its ability to be pressurized. Therefore, the oil warning light may initiate as a simple way of saying that it’s time for an oil change.

Most vehicle manufacturers recommend that the oil be changed every 3,000 miles for a reason. As oil ages, the constant heating and cooling of the engine cause it to break down and lose its ability to lubricate and form a protective layer for engine components.

However, assuming that you are following all manufacturer recommended guidelines and are not overdue for an oil change, there are three scenarios that encompass the majority of oil light cases, which may help explain why it illuminates while braking. We’ll look at each one in greater detail below.

A Faulty Oil Pressure Sensor

The most likely, and, fortunately, the least problematic reason that your oil light comes on when braking is due to a faulty oil pressure sensor.

The oil pressure sensor works to keep track of the oil pressure in the vehicle and transmit this information back to the combination meter or instrument panel. If a calculation falls outside of the acceptable range, the oil pressure warning light will come on.

This is an important function because:

Low oil pressure could mean that insufficient oil is being circulated through the engine, leading to poor lubrication that could cause the engine to grind and seize.
Excessive oil pressure could mean that the oil bay has been overfilled, with the excessive force causing a gasket to burst, leading to a major leak.

The oil pressure in a car will change based on the RPMs of the vehicle. When pushing down on the gas and revving the engine, oil pressure will increase. When braking and lowering the RPMs on the vehicle, oil pressure will decrease.

When an oil pressure sensor goes bad, which will happen over time, it may not be sending information quickly enough to the combination meter or control panel. Therefore, a drop in oil pressure when braking may incorrectly be interpreted as outside of the acceptable range when it is perfectly normal that the oil pressure should go down as RPMs decrease.

What to Do If you Suspect the Oil Pressure Sensor Is Faulty

If you aren’t near an auto parts store to test the cause of the oil pressure light, there is a series of steps you will want to follow:

Pull your car to a stop in a level resting spot and turn the engine off
Give the engine several minutes to rest and let the oil settle
After waiting for several minutes, pop the hood and locate the oil dipstick. This is likely to be located near the front and should have a yellow ring at the top through which to insert your finger and pull
Remove the oil dipstick
Using a paper towel or other light cloth, clean all of the oil off of the dipstick. Check that the oil on your cloth is a light brown color and not overly dark or excessively creamy
Re-insert the dipstick into the oil bay and remove once again
Check near the bottom of the oil dipstick to see if the oil has settled into an acceptable range. The dipstick should have the normal range clearly marked

If the oil levels in your car are at an acceptable level after this initial check, then you can probably feel confident that the problem is related to the oil pressure sensor.

However, there is still the chance that it is the oil pump not sufficiently circulating oil, so you will want to do some further testing to be sure. The following steps should be taken to further troubleshoot the cause of the oil light coming on when braking:

Pop the hood of your vehicle
Turn the engine on
Listen to the sound of the engine. If the oil levels in your vehicle are normal but you hear grinding, ticking, or other strange noises coming from the engine, then it is likely the sign of a bad oil pump and your oil pressure sensor is simply doing its job and letting you know that insufficient oil is being pumped to the engine

After this secondary test, if the oil levels are normal and the engine sounds smooth, then it is extremely likely that your problems are related to the oil pressure sensor. It should be safe to drive your car to an auto parts store and have them connect your vehicle to a computer to let you know if your oil pressure sensor is, in fact, faulty.

If the oil pressure sensor is determined to be faulty, then it is not an overly difficult repair to undertake. New oil pressure sensors can be purchased for under $20 at most auto parts stores and can be replaced, on most cars, using the following steps:

How to Replace the Oil Pressure Sensor

Locate the oil pressure sensor or switch – the part is located on the engine block or cylinder heads for most vehicles. It has a plastic valve mounted to a threaded metal end. If you cannot locate the oil pressure sensor on your vehicle, you will want to consult your owner’s manual to determine the location
Unplug the oil pressure sensor electrical connector – there will be a small wire that attaches to the plastic, female valve side of the oil pressure sensor. Hold the retaining tab and tug to disconnect this wire. Time can cause some dirt and rust to mount, so it may take several tugs and the help of some tools to get this successfully disconnected
Remove the old oil pressure sensor – it will require some kind of wrench to get the oil pressure sensor loose, so make sure you have the proper tools available. It may be helpful to have some lubricant or WD-40 if there is a lot of rust buildup under the hood. After several turns, it should then be possible to unscrew the sensor by hand
Compare the new sensor to the old one – before purchasing the new sensor, you will have wanted to check with the auto parts store to make sure that you got a part that is compatible with your vehicle make and model. Make sure the sides that screw into the engine block are the same diameter and that the threads are the same pattern
Apply thread sealant – after checking that the old and new sensors are the same size; you will want to apply some thread sealant to the new part. As the part comes in frequent contact with pressurized oil, this is a necessary step to protect against leaks. Find a liquid or paste that is compatible with petroleum-based products
Mount the replacement oil pressure sensor – use your hand to screw the replacement part into the engine block or cylinder head. When you can screw no further by hand, use your wrench to tighten the part all the way in
Reattach the electrical connector – make sure that the wire is fully inserted into the replacement part and that the retaining tab is engaged. Once the retaining tab is engaged, gently tug on the connector to ensure that everything is snug and tightly fitted
Test the replacement part – turn on the engine and let the vehicle run for a few seconds, checking that there is oil pressure on the gauge and that the oil light has gone off. If there is pressure and the warning light is off, you will then want to pop the hood and make sure that there is no oil leaking from the area you just worked on

If the oil light does not go off after 10 seconds of running the engine, turn off the engine. This is a sign that the part has not been properly installed, or that there was a much more serious problem with the oiling system. Running the vehicle under these conditions can put thousands of miles worth of wear on your engine in a matter of seconds and cause irreparable damage.

If the oil light stays on after making this repair, or you do not feel comfortable working on your own vehicle, then it is best to have your car towed to a professional shop for further consultation.

A Bad Oil Pump

If the oil pressure sensor is not the cause of your oil light getting triggered, you could be looking at a bad oil pump.

The oil pump circulates pressurized oil to the rotating bearings, the sliding pistons, and the camshaft of the engine. This lubricates the bearings and assists in the cooling of the engine.

Signs Your Pump Is Bad

There are several signs that a defective oil pump could be the cause of your illuminated oil light.

Decreased oil pressure – the oil pump regulates oil pressure. Low oil pressure is a serious problem and puts the health of your engine at serious risk. Vehicles with low oil pressure will have less power, increased engine heat, and higher frequency of stalling out, which could be why your oil light is illuminating when braking
Higher engine operational temperature – oil prevents friction of engine components. As friction causes heat, vehicles with a worn oil pump will be susceptible to overheating. If the temperature gauge on your vehicle increases in conjunction with the oil warning light, pull your vehicle off the road and immediately kill the engine
Unusually noisy hydraulic lifters – a reduction of oil pressure and flow can cause the oil to not reach the hydraulic lifters in the engine. This will cause a lot of noise and wear over time
Noise in the valve train – in addition to hydraulic lifters, the valve train will include pushrods, valve seals, and seals. All of these components need lubrication for proper function. Without it, there will be increased noise
Noise coming from the oil pump – this part should be quiet when operating normally. If the oil pump starts to fail, however, it may begin to make noise. Listen for an unusual whirring or whining sound while the engine is running

While a bad oil pump may keep the oil light on all of the time, even when not braking, there is a chance that the decreased oil pressure that occurs when the RPMs lower could trigger the oil light when applying the brake of a vehicle with a faulty oil pump.

Replacement of an oil pump is probably not a repair to be attempted by a novice. It is a time consuming and involved repair that usually requires the use of a full mechanic’s shop to undertake. The cost of a professional oil pump repair will cost approximately $400 – $500 for most vehicles.

A Leak Somewhere in the Engine

The engine of a traditional internal combustion engine (ICE) vehicle will consist of a series of seals, gaskets, and oil plugs that keep the oil contained. While high oil pressure can prematurely cause a leak from any of these areas, time, cold weather, and normal wear can also cause any or all of these components to fail, allowing oil to leak out.

An oil leak can lead to low oil levels and when oil pressure decreases during braking, there may not be sufficient oil in the pan to lubricate the various engine components, causing the oil light to flash on.

Testing for Engine Oil Leaks

To test for engine oil leaks, place a clean piece of light-colored cardboard under the front of the vehicle. If the cardboard collects a light brown fluid, you are looking at an oil leak.

Using the same process described in a previous section, locate the oil dipstick, and check oil levels. If the dipstick is dry, locate the engine oil bay, remove the cap, and use a funnel to add the appropriate engine oil, described in your owner’s manual.

There may be a temptation, since you are leaking oil, to add “extra” oil to make up for that which is being lost. However, this should not be attempted, as too much oil will increase oil pressure, which will make the existing leak worse, or create a new leak altogether.

If you know that you are leaking oil, it is essential that you check your oil levels every time you set out to drive and that you carry sufficient oil in your vehicle in the event that addition is necessary. Driving a vehicle with low oil levels should not be attempted, as irreparable engine damage is sure to occur.

Like an oil pump replacement, fixing an engine leak is not a repair to be attempted by amateurs. It can be quite difficult to locate the source of the leak, and certified mechanics may need to utilize extensive pressure testing to find where the oil is coming. There is even the chance that your engine may need to be taken to a shop that specializes in engine repairs.

Why Oil Light Comes on When Braking: Final Thoughts

Once you have checked that your oil has been changed according to schedule, there is a high likelihood that the oil light comes on when braking due to a faulty oil pressure sensor. Oil pressure is expected to drop 10 psi for every 1000 RPMs, and this pressure decrease when braking could cause a faulty oil pressure sensor to calculate an acceptable range incorrectly.

If the oil pressure sensor is the cause, the repair is generally simple, straightforward, and affordable. However, if the problem is due to a bad oil pump or engine leak, then you will need to take your vehicle into a professional. Under no circumstances should a vehicle be driven with the oil light on, even if you’re sure that it’s just a bad pressure sensor.

Why Oil Light Comes on When Braking – and How to Fix It