If your car check engine light suddenly disappeared, you could be asking yourself why it went off and whether you should pay your mechanic a visit. What exactly caused the check engine light to just go off?
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The check engine light disappeared because the problem that caused it to come on was remedied on its own without the mechanic’s intervention. It could also be due to an intermittent problem which will come back after a while.
Our complete guide below will discuss more details about the check engine light disappearing on its own, possible causes, and helpful tips on how to deal with this issue.
Why your check engine light disappeared
The check engine light disappears when the issue that caused it to come on no longer exists. This usually happens when the problem resolves itself even without visiting your mechanic.
Remember that your car computer keeps on performing tests on the engine while you’re driving. If the engine passes a test that it failed the last time, then the computer will register the error as resolved and the CEL will deactivate.
The problem causing the CEL to come could be a minor issue such as a loose gas cap or it could be a more serious issue such as the O2 sensor. Other possible causes include loose connections, a sign of failing parts, changes in the surrounding temperature atmospheric pressure, humidity, etc.
A perfect example of such a problem is the catalytic converter efficiency failure code. Your car computer will throw this code.
Then, after a few drive cycles down the road. the system tests the cat converter tests are a bit below the average, making the trouble codes clear on their own and consequently the CEL goes away.
In other cases, your car engine might be experiencing an intermittent fault which will make the light disappear after the issue resolves. This kind of problem may reappear after a while, say up to a week or months, or the next time you start your engine.
Intermittent problems can range from a bad sensor to a purge control solenoid valve that sticks open intermittently when your engine is cold, fuel injector or ignition coil wiring harness connector (the wires could be loose, frayed, broken, or corroded), and even bad fuel.
It is also possible that your CEL just disappeared because its bulb just burned out. Yes, it happens. The CEL is just a light bulb after all and will blow off at some point.
To check if your bulb has burned out, check whether it briefly comes alongside all the other lights on your dash the next time you start your car. If it doesn’t, it means it is blown and you need to have it replaced with a new one.
What should you do after your check engine light disappears?
Our recommendation when the CEL disappears is to have your car scanned for the historic fault codes. This will help you find out the underlying issue.
This is a good idea as you’ll be able to check whether your car is suffering from any other mechanical issues that might grow into more serious issues with time.
You can have a mechanic or go to AutoZone and have them diagnose your car for why the check engine light came on.
A professional mechanic will also look for any “hidden codes” present in your computer. Such codes are usually issued for your car engine and would not make the warning light come on unless certain criteria is met.
In case they find that one of these codes triggered the CEL, then it means the issue hasn’t been solved yet and the CEL won’t appear until the criteria for it to come on is met.
If you can’t find an AutoZone or mechanic who can pull the hidden codes, take your car to the dealership and let them handle the problem.
Overall, you should never ignore the CEL, even if you’re convinced it came on due to a minor problem. Just make sure you have your car scanned for the error codes and find out what caused the light to come on.
Why your check engine light disappeared after refueling
If the CEL disappeared after filling up the fuel tank, this is most probably a gas cap issue. Usually, when the check engine light goes On/Off around the refueling period, it always has something to do with a loose gas cap or a bad gas cap (i.e., it has a damaged O-ring that won’t form a tight seal).
Always make sure you put on the gas cap correctly and ensure it’s tight in position (it ought to click 3-4 times). If the check engine doesn’t go away, then you have a faulty gas cap and you need to replace it with a new one.
If the light comes on again, even after changing the gas cap, take your car to an auto mechanic shop for diagnosis and find out what issue is triggering the check engine light.
Also, if you’re not convinced that a gas cap issue caused the CEL to come on, take the car to an auto parts shop or a mechanic and have them pull the error codes stored in your car memory.
Why your check engine light disappeared after a week
If your check engine light disappeared after a week, it also means the problem has been resolved. Your vehicle computer no longer detects the issue occurring again, after a given number of drive cycles (depending on your car model), so the CEL goes off.
It could be possible the problem was intermittent (in which case the light will come on again after a while) or it was a minor issue.
Regardless of what you think the issue that caused the light to come on was, we advise you to have your car scanned for the fault codes. This is the only way you’ll understand the problem causing the CEL to illuminate.
Having your car diagnosed for error codes also means you’ll also get to find out if there are other problems with your car engine and repair them in advance so they don’t develop into more serious issues in the future and cost you more money in repairs and parts replacements.
Why your check engine light disappeared after months
You may have ignored your CEL for many months on the basis that your car is running smoothly and doesn’t show any problems. This happens all the time and some car owners will go with the CEL on for as many as 6 months or even a year!
Then, one day, after all these months, the light disappears on its own. This is another case of the issue that caused the CEL to illuminate resolving on its own.
Most of the time, the error codes make the light come on automatically reset after a given number of key cycles. This clears the warning light if it was a one-time problem, for instance, leaving the gas cap off or an engine knock.
If after many drive cycles the error code isn’t thrown again, the computer turns off the light which means everything is fine.
However, to be on the safe side, we encourage you to get your car error codes read even after the light disappears. The check engine light came on because the computer detected a problem. And knowing the source of the light is important. By having your car codes read, you may be lucky enough to catch an issue early enough before it becomes an expensive repair.
Still at it, we also advise you against ignoring your check engine light for so long. The CEL is there for a reason, which is to alert you in case of any engine issues.
Whether it’s flashing or steady, you should always have your car diagnosed when it shows up to find out what the problem is and have it fixed on time.
Don’t wait for months for the light to resolve on its own—unless you want it to throw into a mammoth issue and you end up witnessing black smoke coming out of your car engine!
Why your check engine light disappeared after starting car?
Under normal circumstances, the check engine light is supposed to come on for a few seconds and then disappear whenever you start your car. So, there’s nothing wrong with your engine and your car is fine.
The light coming on and going off after a few seconds is simply what they refer to as a “bulb check.” When you turn the key into the ON position, the CEL as well as the other lights on the dashboard should come on to let you know they’re functioning correctly.
You should only be worried when the light comes ON after you start your car and the engine is running.
This means your vehicle diagnostic system has detected a diagnostic trouble code and you should have it scanned to find out what issue the engine is experiencing and have it fixed on time.
If you’re experiencing a check engine light that has disappeared, you may have questions about what caused it and whether you should be concerned. Our article on check engine light diagnostic cost covers some factors that can influence the cost of diagnosing the issue, which can help you prepare financially. Another issue that can cause concern is a check engine light that is flashing but not showing any codes. Our article on check engine light flashing but no codes discusses some possible causes for this issue, which can help you diagnose the problem and take appropriate action.
Frequently Asked Questions:
1. Can check engine light disappear on its own?
A check engine light can disappear on its own if the problem causing it to illuminate has been corrected. As we explained in the above guide, your car computer is always running tests on the engine and if it discovers that the problem that caused the light to come on is no longer available, it will just turn off the light.
2. Should you still have your car checked after the check engine light disappears?
Yes, it is important to have your car checked by a mechanic for error codes even after the light has disappeared. This is important keeping in mind that the light came on in the first place because of a certain problem. The code for this issue will still be stored in your car memory and having it scanned will help you understand what issue your car has and whether it needs to be worked on so the CEL doesn’t show up again.
3. Why did my check engine light come on for a couple of days and then disappeared?
If the check engine came on for a few days and then went off, it means the problem that triggered it has been corrected. The issue is no longer detected by the car computer so it turns the CEL off. in this case, you should have your vehicle checked by a mechanic for fault codes that triggered the warning light.
It is common for the check engine light to suddenly disappear from your dash. The best explanation for this issue is that the problem that caused the light to come on has resolved itself, making the CEL go off. In some cases, your car could be experiencing an intermittent problem and this means the light will keep appearing and disappearing, and finally come on for good and stay in until the problem is fixed.
The good thing is that the trouble code that caused the light to come on is still stored in your car’s memory. So, you should have your car scanned to find out what the problem was. Don’t assume your car is just fine, or the light will pop again after a while. Just book an appointment with your mechanic and have them diagnose your car and advise you on what needs to be repaired.