Check Engine Light Goes On And Off (What To Do About It?)

Check engine light is something that goes on and off is something that a lot of car drivers have experienced. You might be on the road and on your way to work, or you have to go somewhere, and then you notice that you see that your check engine turns on. And then it will then turn off. 

For car drivers, this is a situation that is weird and must be looked upon. If you check engine light is on, it means that there is something wrong with your vehicle. But if there is, it should not turn off after a while, even if you did not do anything to fix it. 

And with that, you would ask yourself why it turns on and then off. If this happens to your vehicle, do not fret. It is a regular thing. It happens more often if you are driving a more than ten years old vehicle. 

The reason can be very simple, and it just needs to be addressed. Vehicles nowadays are made with technology, and sometimes, technology does not last forever. 

So now, we will be talking about checking engine lights that go on and off. Let us get started!

Check Engine Light Goes On And Off

What Is A Check Engine Light?

A check engine light that is turned on can be because of a minor issue. Issues include a faulty gas cap, or it can also mean something more serious, like a misfire on your engine. You then have to go to a mechanic to have your vehicle fixed. The engine check light is the malfunction indicator lamp (MIL). 

The check engine light comes in orange, amber, or yellow, depending on the manufacturer. If the light starts flashing, this can mean a more severe problem. It can be a misfire, quickly overheating the catalytic converter. 

Why Check Engine Light Goes On And Off?

Check engine light goes on and off, and many car drivers can experience it. The reason for this issue can be simple, but you might need to visit the nearest mechanic in your area. They can prevent your vehicle from future check engine lights turning on by fixing the issues. 

Unfortunately, this can mean resetting your vehicle’s ECU because the ECU is the main computer, and it controls everything. But here are the possible reasons why your check engine light goes on and off. 

1. You Might Have A Loose Gas Cap

You might have a loose gas cap, and it can cause disturbance for the check engine light. If you do not tighten the gas cap, it can cause the engine light to come on. The engine light will also stay on until you tighten your gas cap properly. 

You also need to check your gas cap if there are any issues regarding your gas cap. You have to check for any crack, or there might be uneven fitment if the cap is already old and needs replacement. You can get a new gas cap because they are affordable. 

2. You Might Have A Bad Oxygen Sensor

This can be an issue. Oxygen sensors can be mounted on the front part of the exhaust just right after the manifold. 

These play an essential role in seeing how much of the exhaust gas is coming out of the exhaust. They will scan the data and send it to the ECU that will check the data and then provide the right fuel to air mixture in the engine. 

3. You Might Have A Bad 02 Sensor

An alarming 01 sensor can cause a sensor to your vehicle so that it can run rich in fuel. So it’s better to address this problem as soon as possible because your vehicle needs to run correctly even without issues. If you do not fix this issue and do not solve your check engine light, it can be permanent to your dash. 

The oxygen sensors are pricey if you will get a decent brand. If you want it to last, do not go for cheap ones because they can break after some time. As a result, your vehicle will be broken down again.  

4. You Might Have A Bad Spark Plugs

Bad spark plugs can go wrong after thirty or more thousand miles, and they can show the check engine from time to time. This will happen if there is no rough spark in the combustion chamber and the fuel is not ignited. This can cause your vehicle to drive poorly and cause your vehicle not to start. 

There is no rough spark in the combustion chamber if the fuel is not ignited. This can also cause your vehicle to run bad, so you have to change your spark plugs to solve your problems. 

5. You Might Be Having A Bad Mass Airflow Sensor

A mass airflow sensor, known as the MAF, is well known to go wrong after many miles, and it can cause some check engine light on your dashboard. The mass airflow sensor controls how much air is inserted into your engine and will send data to the ECU. This is a significant role that the sensor will play. 

You might not even start your vehicle if it is ruined, so you need to fix your sensor. You should also buy a suitable quality sensor from a good manufacturer so that your sensor will last. 

6. Your Exhaust Gas Recirculation Valve Can Fail

Your EGR valves or exhaust gas recirculation can fail. If you have one on your vehicle and get the check engine light, this can be the cause. They have a role in decreasing the amount of nitrogen oxide coming out of your engine. 

This will keep it running efficiently, and it can also reduce emissions. However, these valves can get clogged up easily after one hundred fifty thousand miles and fail. 

What To Do When The Check Engine Light Goes On And Off?

If your check engine light is coming on, some people try to ignore it, but some people want to turn their check engine lights off. First, you should have your vehicle seek the services of a mechanic. 

Mechanics will use a unique tool, and they will pull the codes from your vehicle’s central computer and tell you what is wrong with your engine. For example, you might have a loose gas cap and a faulty mass airflow sensor. 

Frequently Asked Questions

These are the frequently asked questions about check engine light that goes on and off. 

Check Engine Light Turns On And Off Randomly

Your check engine light can turn on and off because you might have an intermittent issue with some of your vehicle’s systems. There might be some error codes that will make the light turn on, and the light will stay turned on until someone uses a code reader to get cleaned. 

If your check engine light is turned on, you can have someone read the codes out of your vehicle. A lot of auto stores will do it for free. 

Check Engine Light Comes On And Off With No Codes

The top common cause of the check engine light is a missing or a lousy fuel filler cap. If the code is related to the fuel system vacuum or pressure, you can do a simple repair yourself. You can buy a new cap and reset the code with the same ODB-II scanner. 

Check Engine Light Turns On And Off Periodically?

There is a loose gas cap, which can cause a disturbance and check engine light. If you do not tighten it, the light can come on, and then the check engine light will turn on until you tighten your gas cap properly. You also need to check your gas cap if there are issues. 

Check Engine Light Goes On And Off Randomly: O2 Sensor?

A check engine light can turn off by itself if the condition is causing it to be fixed. If this comes on, it might mean that one of the vehicle’s systems, ignition, emission control, fuel injection, or emission control, might function correctly. However, it will reduce the efficiency of the engine and the performance. 

Check Engine Light Goes On And Off Randomly: Catalytic Converter?

The catalytic converter might be failing. The catalytic converter is a critical part of your exhaust system, and if there is no catalytic converter, you’ll not pass the emissions. They are the ones that purify the exhaust gasses that go out of your exhaust. 

They will block the Nox particles. With that, they will make your vehicle run cleaner and safer for the environment. The bad side of these catalytic converters is that they can clog up. 

If they do, it can be costly to place them. They will go bad after a few miles, and they can trigger the check engine light. 

Check Engine Light Goes On And Off Randomly: Knock Sensor?

There can be problems with your knock sensor, and it can put the check engine on. You can consult a mechanic to fix the issue for you. 

There can be some fault with your knock sensor. It would be better to fix it with an expert than do it independently.


In summary, many car drivers experience their check engine light turning on and then turning off. This is not unusual because it is normal and can be experienced by car drivers. 

You have to fix the issue causing your check engine light to turn on and then turn off. If you are done fixing it, it will go back to normal.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more