Skip to Content

Why Is My Oil Light on When It’s Full?

Few things can give a driver as much stress as a flashing oil light indicating low oil. It’s probably the last thing you want to see, and it can be more of a concern when you recently stocked up on oil. So, why is your oil light on even when the oil levels are full? 

Your oil light is on when the oil is full due to a broken pressure sensor or a damaged pump. A broken oil pressure switch, a dirty oil filter, and contaminated oil may also cause the light to stay on, even when you’re stocked up on oil. In the worst-case scenario, your engine may be leaking.

This article will look at each of these causes in detail. I’ll also explain how to recognize what’s causing the issue and how to fix it, so let’s get started! 

How To Fix and Identify Why Your Oil Light Is On

If you’ve just filled the oil, but the light stays on, it could be due to various reasons. However, in most cases, it’s a sign that the oil pressure sensor is faulty. If the problem is with the pressure sensor or wiring that connects the sensor to the oil meter, there’s no need to worry. 

However, if the problem is a mechanical one that’s caused by a clogged oil filter, dirty oil, or a damaged switch, you’ll have to fix it immediately. If a leak in your car is causing your oil levels to plummet, avoid driving your car, or you could permanently damage the engine.

Let’s explore the reasons we’ve outlined here in greater detail.

1. The Oil Pressure Sensor Is Faulty 

A faulty oil pressure sensor is probably the main reason why your light is on, although you’re sure you’ve just filled the oil.

This sensor is responsible for measuring your oil levels, and if it registers a reading less than what’s required for proper engine function, the light will turn on.

However, sometimes this sensor may get damaged or worn out and register an incorrect reading. While this isn’t a major problem if your oil tank is full, it can become a problem if the oil levels are low and the sensor doesn’t detect any change.

In some cases, there may not be anything wrong with the oil pressure sensor, but the wiring connecting it to the dashboard may get loose or damaged. Fixing this problem is pretty straightforward, although pinpointing a loose wire can be difficult.

A faulty sensor isn’t a major problem and can quickly be diagnosed with a vehicle scan. If your oil pressure sensor is damaged, you can manually assess your oil levels but fix the sensor immediately.

How To Fix

If your engine has a damaged sensor, you’ll have to replace it. If the wiring is damaged or loose, you can replace the wiring or have a mechanic fix the problem. Wiring problems are usually easier (and cheaper) to fix with professional help since you’re only paying for labor costs. 

However, if the pressure sensor is defective, you’ll have to buy a replacement and pay for the labor costs involved with installing it. Unless you’re a mechanic, don’t try to replace the sensor yourself.

You’ll never know whether the ICP sensor is damaged or if the problem is with your oil pressure sensor or another component. And without the right knowledge, you can make the situation worse.

Fortunately, replacing the pressure sensor is a relatively inexpensive affair, but ensure you use the original parts. 

2. The Oil Pump Is Damaged

A faulty oil light could also mean the oil pump is damaged. This problem is serious as the oil pump ensures that all engine parts get enough oil. When there’s an issue, your engine won’t get adequate oil, even when filling it up. 

A damaged pump may also be why your vehicle’s oil light is on, even though the oil is full. Unfortunately, this is a major problem because it can cause permanent engine damage if it isn’t rectified soon.

A faulty oil pump may also result in your engine overheating because there’s less oil in circulation. If the oil pump isn’t circulating oil at all, you may not be able to start the engine, and you might hear strange noises.

If you realize that there’s a problem with your oil pump, fix the issue immediately, or you may have to replace the whole engine!

How To Fix 

Like with the sensor, the only way to resolve an oil pump problem is to replace the pump. Replacement is essential because the pump will only get damaged if worn out, making matters worse.

Oil pumps are more expensive to replace and usually cost an average of $500. However, it’s a critical component of your engine, and you should completely avoid starting your engine after finding out that the pump is damaged. 

Replacing an oil pump is also much cheaper than replacing the entire engine, and that’s what you’ll be looking at if you continue driving with a faulty oil pump.

3. The Oil Pressure Switch Is Damaged 

Sometimes there may be nothing wrong with the oil pump or pressure sensor. However, the switch that signals your oil levels may be damaged. Since this switch connects the dashboard light to the sensor, the light may stay on even when oil levels are full.

As with a damaged oil pressure sensor, a faulty oil pressure switch isn’t a major problem if your engine oil levels are good. However, when the oil level is low, a faulty pressure switch may not alert you of the same, and you risk overheating and damaging the engine. 

How To Fix 

Replacing the faulty oil pressure switch will instantly solve this problem, but diagnosing this issue on your own can be difficult. As such, it’s best to take your car to a mechanic to have the oil levels checked and find out if there’s a faulty switch.

Fortunately, an oil pressure switch is easy to replace, and you won’t have to pay much apart from labor costs. 

4. The Oil Is Dirty, Or the Oil Filter Is Clogged 

Dirty or contaminated oil is a lot worse for engines than you can imagine, which is why changing your oil on time is crucial. And while pure engine oil can be expensive, it’s a lot safer for your car than second-grade options from shady dealers.

In fact, using engine oil that doesn’t meet certain standards can damage your engine parts and even cause your oil light to stay on when the oil is full.

The problem with bad engine oil is that it contains rough particles and contaminants that may cause blockages and prevent the oil from circulating properly. 

A circulation problem may also occur when the oil filter is clogged. This issue may be caused if you don’t replace the filter on time, but it can also be due to dirty engine oil. 

If your engine oil is so bad that the engine light is on when the oil is full, you’re well overdue for a replacement, so don’t wait! The dirty oil can seriously damage your engine, leading to further complications down the line.

How To Fix 

To avoid dealing with bad engine oil, replace the oil after the recommended mileage is completed. You’ll also have to replace the filter with every service to avoid clogging and other problems.

How many miles you drive before needing an oil change will depend on the type of oil and your vehicle. 

However, most experts recommend changing your engine oil after 7,000–12,000 miles (11,265-19,312 km) if you’re using regular synthetic engine oil. An oil filter only needs to be changed after every second oil replacement, which is usually after 14,000–20,000 miles (22,530-32,186 km). 

5. The Engine Is Leaking Oil 

A leaking engine is the worst possible cause of a faulty oil light. In some cases, you may fill up your car with oil and find that the light is still on. If that’s the case, you may have an oil leak on your hands.

You can check this manually to see whether oil levels have actually dropped. Low oil levels are extremely dangerous as your engine may overheat, or the delicate parts may get damaged. 

How To Fix

For this situation, you’ll need an experienced mechanic since there can be hundreds of problems causing your engine to leak oil. Call a mechanic immediately if you notice a leak, and avoid driving your car. 

Don’t be fooled if you don’t see oil dripping from your engine. It could be that the oil dried up or that the leak is minor, so you haven’t detected it yet. If there’s a misplaced washer or valve, fixing the leak won’t cost much.

However, if the problem is bigger and your engine is damaged, be prepared to shell out quite a lot.

Final Thoughts 

While you can check the oil levels manually to confirm for yourself, it’s not a good sign when your engine light is on.

Always call a mechanic to diagnose and fix the problem to prevent serious engine damage. It’s a small investment to prevent bigger (and more expensive) issues in the future.