Check Engine Light Comes On And Off

Check Engine Light Comes On And Off – What’s Causing It?

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 strange behavior. Because everyone knows that a 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 a 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 is easily addressed by a professional mechanic in no time, or even by yourself if you have the right equipment.

Check Engine Light

Check Engine Light Comes On And Off

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 are 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 spark plug, 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 fix 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 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’s 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.

Check Engine Light Comes On And Off

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:

Check Engine Light Comes On, Potential Causes #1: Bad Ignition Coils

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 to 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.

Check Engine Light Comes On, Potential Causes #2: Malfunctioning Fuel Injectors

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.

Check Engine Light Comes On, Potential Causes #3: Bad Thermostat

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.

Check Engine Light Comes On, Potential Causes #4: Faulty Catalytic Converter

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 gases that go out from the exhaust.

They block the NOx particles and make the car run cleaner and 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.

Check Engine Light Comes On, Potential Causes #5: Bad PCV Or EVAP System

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 a 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.

Why Does My Check Engine Light Come On And Off

If this is the case you shouldn’t be worried, these problems may appear to any car owner. Some of these potential reasons are so simple, that you may even laugh at them at first. 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 illuminating the check engine light in the future. 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:

Check Engine Light Comes On Off, Causes #1: Loose Gas Cap

A loose gas cap, although hard to believe and also sounds funny. Something like a loose gas cap may cause a disturbance in 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.

Check Engine Light Comes On Off, Causes #2: Bad O2 Sensor

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.

Check Engine Light Comes On Off, Causes #3: Worn-Out Spark Plugs

Bad spark plugs. Spark plugs know to go bad after several thousands 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.

Check Engine Light Comes On Off, Causes #4: Malfunctioning MAF Sensor

Bad mass air flow sensor. Mass airflow sensors or shortly known as MAF are well known to go bad after many miles, and also cause some check engine lights on your dashboard. The mass airflow sensor is controlling how much air is inserted into the engine and sends that data to the ECU.

This 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.

Check Engine Light Comes On Off, Causes #5: Faulty EGR Valves

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.

This also 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 Check Engine Light To Come 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.

How To Fix A Check Engine Light

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 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.

Step 1:

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.

Step 2:

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.

Step 3:

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 advanced 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.

Step 4:

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.

Step 5:

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 on 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 for how to replace spark plugs and there are plenty of sources out there that will help you out.

Step 6:

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.

Step 7:

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 given 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.

Step 8:

A bad EGR valve, as it’s one of the main issues for this headache. If you are into mechanics you will search for ways 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.

Step 9:

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.

Can You Drive With Check Engine Light On

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 The Check Engine 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.

Essential Facts

  1. Check engine light is a yellow or orange light that appears on your car’s dashboard when your car is having a problem.
  2. The check engine light does not always mean that there is a serious issue with your engine, but it does usually indicate that there’s something happening with your car that you’re going to need to fix sooner rather than later.
  3. The most common car problems that will lead to a check engine light coming on and staying on include bad ignition coils, bad fuel injectors, bad thermostat, bad evaporative emissions purge control valve, and bad evaporative emissions purge solenoid.
  4. A loose gas cap could cause a check engine light on and off intermittently. You should try tightening your gas cap first anytime your check engine light appears.
  5. A faulty oxygen sensor can cause a check engine light on and off intermittently. It’s important to get it fixed, as it can lead to serious engine damage.
  6. Bad spark plugs can affect your engine’s combustion process and lead to a check engine light on and off intermittently.
  7. A faulty mass airflow sensor can lead to reduced fuel economy, damage to parts like your spark plugs, your oxygen sensor, and possibly even your catalytic converter, and a check engine light on and off intermittently.
  8. It’s important to seek the services of a mechanic when your car’s check engine light comes on and not ignore it.
  9. If you have a check engine light on and off intermittently, you should still get your car fixed as the problems you’re experiencing could be just as bad as the problems that someone with a check engine light that is consistently on is experiencing.
  10. Selling a car with a check engine light on and off intermittently or a check engine light on all the time is possible, but you should disclose the issue to the buyer.


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.

Frequently Asked Questions

If you’re still curious about why your check engine light comes on and off, our FAQs here might help…

Why Is My Check Engine Light On

Your car’s check engine light may come on due to numerous reasons. Most of the time, it pertains to either your car’s engine or its emissions system. For example, a bad set of ignition coils or worn-out fuel injectors and spark plugs may prompt the check engine light to appear. Besides that, a malfunctioning thermostat, as well as bad O2 and MAF sensors (among many other sensors on your car) would also illuminate the check engine light if they failed. Otherwise, you might be seeing a check engine light because your catalytic converters are failing. Alternatively, it might be due to a clogged EGR valve, faulty EVAP, or broken PCV system. Even simple issues like a loose gas cap may prompt the check engine light to appear.

What Does Check Engine Light Mean

A check engine light is also sometimes known as the Malfunction Indicator Lamp (or MIL). Its function is as the name implies, it’s a warning light that appears to alert you if something’s amiss with your powertrain. For almost every car, it’s normal to see the check engine light (or CEL) appear when you’re putting and twisting the key in the ignition slot to turn your car on. However, under normal circumstances, the CEL should disappear in a few moments once your car has started. If the check engine light is still turned on, then it’s an indicator that your car has detected a fault. Thus, it’s a warning that you should diagnose whatever issues it’s found and have them fixed right away if it’s urgent.

What Does Service Engine Soon Mean

While all cars have a check engine light, some vehicles feature an additional warning light known as the Service Engine Soon light. In summary, a service engine soon light is often not as serious of an alert as the check engine light. While the check engine light turns on when serious issues are found, your car will turn on the service engine soon light if a lesser and more inconsequential problem is noted. Usually, these problems aren’t serious enough to cause significant damage to your car if not fixed soon. Besides that, some automakers also incorporate the service engine soon light as a reminder that your car’s scheduled service is due.

What To Do When Check Engine Light Comes On

First off, try to assess the status of the check engine light. If the check engine light is merely turned on and is illuminating in a yellow or orange color, it’s usually not something too serious. However, if the check engine light is blinking/flashing and is lit up in red, then you’ll have to get it diagnosed by a mechanic right away. There are some things that you can do to narrow it down and find what’s caused it to appear. Begin by seeing if there are any other warning lights or messages on your dashboard. For instance, if your car has low oil pressure or if it’s overheating. Then, try tightening the gas cap, as this may cause the check engine light to turn on. Other than that, you can plug in an OBDII diagnostics scanner to extract any error codes that’ll point you to the underlying issue.

How Long Can You Drive With Check Engine Light On

Whenever you’re seeing the check engine light illuminated on your dash, it’s often a bad idea to just ignore it and keep on driving. Although, this isn’t always the case. It ultimately depends on the seriousness of the problem that prompted the check engine light to appear. For example, if the check engine light is turned on but stays steady or is lit up in a yellow or orange color, it’s usually not something serious. Thus, if your car isn’t driving or behaving oddly, you may even be able to drive up to 50 or even 100 miles before sending it over to a mechanic. However, if the check engine light is blinking/flashing or is lit up in red, it’s normally telling you that a serious fault has occurred. To prevent imminent damage to your engine, it’s wise to send it over and have it checked ASAP.

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