Check Engine Light

Check Engine Light Comes On And Off – Why is this happening?

You are probably on the road to get to work or on a trip and suddenly a check engine comes on, then after a few moments later it shuts off. This may be considered as a strange behavior. Because everyone knows that check engine light usually means that something is terribly wrong with the vehicle.

But in this case, it shuts off after a period of time, strange, isn’t it? And you are asking yourself the question why my check engine light comes on and off?

Well, let me answer your question, it’s not a big deal if this happens to you. It is a normal thing especially if you are driving some car that is more than 10 years old. The problem is usually something simple that needs to be addressed.

Cars nowadays are filled with technology and this technology has a lifespan. When a part passes a certain age or miles, it can cause situations like this to happen. These are situations where you are not seeing a problem, but still there is something you need to do in order to take care of this issue.

The most probable culprits for this issue usually are bad sensors, faulty spark plugs, or ignition coils. These things are not meant to last forever, and especially when the car is not driven regularly, they know to break and cause some headaches for car owners.

The most important thing is that it’s not something critical. It be easily addressed by a professional mechanic in no time, or even by yourself if you have the right equipment. In this article, we are going to dive deep into these issues and explain everything you need to know, so follow along.

What Is a Check Engine Light?

Before we dive deep into this topic let’s discuss some basic things. For the people that saw their first check engine light and are still beginners when it comes to cars. This will help them learn about these things. If you are one of those people that still haven’t seen it, good for you because for some of us that is a basic routine.

The check engine light is a special indicator installed in your cluster. It has a function to turn on when there is something wrong with your power unit. This orange light usually appears and turns on when you put the ignition key along with other lights. After you start the car it goes away immediately. But only if the car is in perfect shape and doesn’t have problems. If it does have a problem. This light is going to haunt you until you say it’s enough and decide to get rid of it and visit a mechanic.

Although when people see this light many of them presume that there is something really bad with the car and something seriously went off. But that doesn’t need to be the case. It can be something simple as a sparkplug, or your gas cap may not be fully shut.

It is important to address this issue immediately. If you leave it on and pretend like you don’t see it something seriously may go wrong. You may be left stranded by the end of the road. And you will scratch your head about why you didn’t fixed this sooner.

So, don’t be that guy and when you see this light, it needs to be checked quickly. Go to your local mechanic or do it DIY, something that we will discuss later in this article.

What Causes The Check Engine Light To Come On?

Since we explained more about the check engine light and its purpose now let’s dive deeper into the problematics. Let see what causes a check engine to come up in the first place. There are quite a few reasons and protentional culprits for this problem. Some of them are very serious and some of them are not that potentially dangerous for your engine’s overall health.

First, let’s take aside the things that make the check engine light turn on and stay that way. This is a bigger issue than a flashing check engine light. These problems may cause severe engine damage if left untouched. Some of them are:

  • Bad ignition coils, coils are known to go bad especially if the car doesn’t run that often and is left unused. Bad coils may cause your engine to run rough and unbalanced because there is not enough spark to burn the fuel. When the engine is misfiring, you can notice right away if it runs unevenly. The solution for this problem is a new ignition coil. They are not very expensive and you can do it by yourself at your home. But if you want to save yourself from future headaches it’s best to change all of the coils in your car. This can come up to a big price but the car would run perfectly for a long time.
  • Bad fuel injectors, injectors can also go bad and these can cause some big issues when they are broken and your engine may run rough or don’t run at all. They are a crucial part of the ignition system. Because if you do not have injectors that pump in fuel in the cylinders at the right PSI of pressure, the car will not run as it used to and you may lose power and it can leave you stranded. So, if this is the issue a new injector will be the solution. Injectors come at high prices, especially if you drive a diesel car or truck. They can cost a few hundred dollars and more, mostly because they are a piece of high precision machinery. But there are also a ton of companies that repair these injectors for a fraction of that price and you can go with that option.
  • Bad thermostat. Thermostats are known to go bad after some time. It is smart to replace them when you do your water pump service. A bad thermostat may cause your car to overheat, and this heat may warp your engine block and the head of the block. Especially if it’s aluminum. This can cost you hundreds or even thousands of dollars to fix. If it goes that bad that the engine is destroyed you will have to go on the market for a new engine. Depending on the car it may be very pricey.
  • Catalytic converter failure. Catalytic converters are an essential part of your exhaust system, without them, you will never be able to pass emissions. They basically purify the exhaust gasses that go out from the exhaust. They block the NOx particles and make the car run cleaner and be safer for the environment. The downside of these catalytic converters is that they clog up and it can be a very expensive fix to replace them. They can go bad after many miles and can trigger the check engine light in the cluster. Replacing them sometimes is not a solution, and thankfully there are companies that clean these catalytic converters with high-pressure water and they can be good as new unless they are too far gone, in that case, you will need to open up your pocket and get a new or used one.
  • Bad PCV valve. This check engine light that doesn’t shut off can be caused by a bad evaporative emissions purge control valve also known as PCV valve, which is easy and cheap to fix DIY. A small thing that causes many headaches for car owners.
  • Another reason may also be a bad evaporative emissions purge solenoid.

To sum up, if any of these issues are happening to you the engine light will be on all the time, if it flashes or it is on from time to time it is probably one of the issues that we are going to discuss in the next chapter.

What if the check engine light turns on and off intermittently?

If this is the case you shouldn’t be worried, these problems may appear to any car owner. And some simple things can cause them that you are going to laugh about. Although the cause of the issue may be simple, there is still the need for you to visit the local mechanic to fix these issues and also prevent your car from future check engine lights to appear, and by this, we mean resetting the ECU of the car which is the main computer that controls everything, but first, let’s see what some of these issues are:

  • Loose Gas Cap, although hard to believe and also sounds funny. Something like a loose gas cap may cause a disturbance as the check engine light. If you don’t tighten it all the way it may see the light come on, and the check engine light will stay on until you tighten your gas cap properly. Also, check your gas cap for some issues. There might be cracking and uneven fitment if it’s some old cap that has seen better days. If the gas cap is bad just get a new one, they are really affordable.
  • A bad Oxygen sensor, now this may be an issue. Oxygen sensors are mounted on the front part of the exhaust right after the manifolds. They have an important role and that is to see how much exhaust gas is coming out of the exhaust. They scan the data and send it to the ECU that checks the data and provides the right fuel to air mixture in the engine. A bad O2 sensor may cause your car to run rich on fuel. So it is better to address this problem right away because this is important for the car to run properly without issues. If you delay this problem and don’t solve it the check engine will be permanent on your dash. Oxygen sensors are known to be expensive especially if you get a decent brand. Best advice, don’t go for the cheap ones, they will break after some time and your car will be broken again. Don’t save money on important stuff like this.
  • Bad Spark Plugs. Spark plugs know to go bad after 30 or more thousand of miles, and they also can show you the check engine light from time to time. This happens because there isn’t enough spark in the combustion chamber and the fuel isn’t ignited. This may cause your car to run badly or don’t even start, so replace your spark plugs if you want to solve your problems and avoid getting stranded somewhere where you don’t want to.
  • Bad Mass airflow sensor. Mass airflow sensors or shortly known as MAF’s are well known to go bad after many miles, and also cause some check engine lights at your dashboard. The mass airflow sensor is controlling how much air is inserted into the engine and sends that data to the ECU and that is a very important role that this sensor plays. If it’s completely broken you won’t be even able to start the vehicle, so fixing this sensor is a must. Always buy a quality sensor from a well-known manufacturer if you want your sensor to last and avoid paying twice.
  • Exhaust gas recirculation valve. These valves are also known as EGR valves, and they are prone to many failures. If you have one on your car and you get the check engine light, this is probably the culprit for this situation. They have a role in lowering the amount of nitrogen oxide that comes out of the engine and keeps it running efficiently in the process and reduces emissions. These valves easily get clogged up after 150 thousand miles and fail at this point. If you are into mechanics, you can take the valve away and give it a deep clean. If this works great, if it doesn’t you will have to spend around 150$ for a good quality OEM one.

Can Low Oil Cause This Check Engine Light To Turn On?

A common misconception is that if you run low on oil may cause the check engine light to come on. Many people believe in this, and let me tell you, it is wrong. Check engine does not have any connection with the oil level at all, check engine light usually turns off if there is something wrong with the ignition and the sensors.

For the oil level you have the dipstick that you can check and if you are not into that, or your car does not have a dipstick. If that’s the case an oil light will come on and warn you that you are running low on oil. Also, if you are doing your services regularly, the car will remind you when it’s time for your next service on the cluster and will ask you to visit an official mechanic for your specific vehicle.

Can I Fix This DIY?

Nobody likes to have issues with their car and many people are more inclined to work on their vehicles rather than to pay a professional mechanic to do the job for them. Some of the people are doing this from the economic perspective of saving money. Others like me do it from passion and do not let anyone else touch their car. If you are one of those guys you will probably enjoy reading this.

Check Engine Light Comes On And Off

We are going to discuss some troubleshooting on how you can do this work at home with no expensive tools. Just simple DIY troubleshooting methods that will probably help you if your car has a check engine light that comes on and off, so follow along.

  • If your issue is caused by something trivial the easiest fix is probably removing the positive cable from your battery. By removing this cable, the computer will shut down and when you put the cable back on it should reset itself and should clear the codes. This is the simplest thing to do and one of the easiest fixes out there.
  • If the problem persists then you will need to grab an OBD2 scanner tool. These come cheap and will help you troubleshoot your issue, you will be able to clear the error and move on from there. When you start your car the check engine light should be gone and if it persists and reappears again, there is something more to it.
  • If your OBD2 tool is giving you the codes then search for them online to learn more about them. You need to do this research in order to get to the main issue. If you don’t get the codes on this OBD2 scanner you need to get a more advanced one. An advance scanner has more options and will allow you to dive deeper into the errors and will show you great detail of information. With this tool, you will be 99% sure that you will get the error.
  • If you found your problem, now is the time to deal with the issue. If there are bad sensors replace them with OEM parts, not get the cheap ones because you are going probably have to pay twice in the near future because low-quality sensors are not good.
  • If it’s something with the ignition like spark plugs, coils, injectors. All of these things need to be addressed as soon as possible. You don’t want to get stranded by the road. More on that how you can replace these parts you can find online and there are some detailed guides on how to do this. Just search on YouTube how to replace spark plugs and there are plenty of sources out there that will help you out.
  • If it’s the PCV valve, just replace it with a new one. This is a simple and easy task to do, especially if you are into cars.
  • If the catalytic converter is bad then you need to get a used one or just find a service where these catalytic converters are cleaned and give it a good service. It should come out as brand new when they are done with it. If it’s too far gone you will need to replace it with a new one.
  • Bad EGR valve, one of the main issues for this headache. If you are into mechanics you will search for ways on how to remove it from the engine and then give it a good clean, if it doesn’t work you will need a new one or just get an EGR delete, and remove it completely.
  • For all of the things we discussed above to work you need to clear off all of the codes after you are done with your car. Then the check engine light should be gone.

Should I Just Ignore It And Drive The Car As It Is?

You should definitely not be driving your car as it is. Just take it to your local mechanic. If you have the know-how and the right tooling then try to fix it on your own, although I would still recommend a professional mechanic. Especially if you do not know what you are getting into.

Can You Sell A Car If This Light Is On?

You can try, but not many people would like to buy it from you. Especially people that are not mechanically inclined and are not into troubleshooting problems to find a fix. Even if they like to buy the car from you, they would love to get it at a cheap price. So better fix the check engine light before you sell.


In this article we went deep and learned a lot about this issue with the check engine light that comes on and off. We also thoroughly explained the main culprits for this issue. And finally, we shared some DYI fixes that will make your life easier. If you are a beginner, it is better to leave it to someone that is more experienced to deal with these issues, like a mechanic. But if you think you are ready just dive into it and start doing some troubleshooting.

Approved Tools

These tools have been tried and tested by our team, they are ideal for fixing your car at home.

1 Comment

Leave a Reply

Your email address will not be published.