Check Engine Light Turned off by Itself – Here’s Why

If the check engine light comes on, the light usually indicates there’s an issue. It could be a minor issue, or it could mean something more serious. However, it usually means you’ll want to take your car to a professional to have it diagnosed and the potential issue repaired to avoid further damage. But before having the chance to address the cause, the check engine light turned off by itself without you doing anything. So you might ask, can check engine light turn off by itself, and is the issue fixed?

In this article, we’ll answer more in detail if a check engine light can turn off by itself and why. But also what you should do next. Keep reading!

Can Check Engine Light Turn Itself off?

A check engine light can turn off by itself if the problem that caused the light has been corrected. Your car’s computer is regularly running tests to find issues, and the light will illuminate on your dashboard if your vehicle fails two tests in a row. So if the check engine light turns itself off, it means it passed.

But before jumping into why the check engine light turns off by itself, you need to understand why it first came on.

What Does the Check Engine Light Mean?

The check engine light is one of the most common dashboard lights.

Your car’s computer is always running tests as a part of your vehicle’s On-Board Diagnostic system. It includes both continuous monitoring of such as the engine timing and misfires and non-continuous monitoring of other related components that could increase emissions, like the catalytic converter or small vapor leak.

When speaking car language, mechanics and car enthusiasts sometimes talk about a “two trip monitors” when discussing warning lights.

It means a check engine light, usually yellow, orange, or amber, will pop up on your dashboard if your car fails two tests in a row.

However, there’s no way to say why your engine light is illuminated, and to know what is wrong, it’s best to let a professional diagnose the issue.

Why Did My Check Engine Light Turn off by Itself?

Usually, the check engine light stays on as long as the root of the problem is still present and your car keeps failing tests.

Whether that is because of an EVAP system leak, such as a loose fuel cap that allows fuel vapors to escape, a catalytic converter failure, or an incorrect air-fuel ratio, the light will stay on until the issue is fixed.

However, many drivers think a check engine light reset is necessary, but sometimes you don’t have to do anything at all.

Let’s say that your check engine light comes on. After a week, you are about to take your car to a mechanic, but on your way there, the check engine light turned off by itself.

It means that during this drive, your car diagnostic system performed three tests that your car passed.

Great! You turn back home thinking you no longer have a problem, which may be true. However, it’s always best and recommended to take your car to the mechanic anyway for diagnostics.

Something caused that light to turn on in the first place, and the technicians can read the trouble codes with an OBD scanner to see what and why the test failed.

Another common scenario is if the check engine light went off after getting gas, then the cause of the light was probably a loose gas cap. 

The Evaporative Emission Control System (EVAP) in your car monitors the pressure in the fuel tank during a drive cycle and checks for leaks to let you know if you have gas fumes escaping.

The gas cap has a seal that makes the fuel tank airtight, but if there is a leak of pressure in your gas tank, the check engine light will pop up.

And maybe you even noticed your car smelling like gas lately. But after putting back your gas cap, you probably tightened it enough to seal it properly and the light went off.

Is It Safe To Drive With Check Engine Light On?

Usually when an warning light illuminates, you get a bad feeling in the pit of your stomach. But does it mean it’s not safe to drive?

If the check engine light comes on and you notice any changes in how your car runs, it is best to pull over and call for help. However, if the light comes on and nothing seems to be wrong, it’s likely caused by a simple mechanic failure or a non-invasive sensor that has failed. It means it is safe to continue driving without additional damage.

But the light might causes your car to enter a security feature known as “limp mode.” It can cause the less essential parts of your car to switch off and cause restrictions to the car’s performance to make sure that you won’t blow or damage any engine parts.

Either way, you should troubleshoot for issues or causes as soon as possible. Being stupidly stingy and turning a blind eye to the problem rarely pays off in the end. And you wouldn’t want to drive around in limp mode more than necessary.

Why a Mechanic Isn’t Able to See the Issue

If the light is turned off and the mechanic runs diagnostics but won’t be able to see any error codes, it’s because your car has passed the same test more than 40 times. Not all car models have this feature, but some car manufacturers such as Audi and Volkswagen do.

Should I Still Get My Car Checked If the Check Engine Light Turned off

It’s recommended you still get your car checked even if the light is turned off. As mentioned earlier, something caused that light to turn on in the first place, and it’s a good idea to check for trouble codes.

Can I Diagnose the Problem Myself?

Yes, diagnosing the problem yourself with an OBD scanner is possible. They are easy to use, and you can buy one for around $100.

Here’s a guide on How To Use an OBD Scanner for beginners from mycarly.com.

However, most auto part stores (such as AutoZone, Advance Auto Parts, and Pep Boys) will provide a free diagnostic code reading or let you borrow an OBD scanner with instructions for free.

Here are some of the trouble codes to expect.

  1. Oxygen Sensor Code (P0171-P0175): You will get this error code when it detects a problem with the oxygen sensor. This sensor gives your engine computer information about the amount of oxygen in the exhaust. The error codes (P0171, P0173, P0174) indicate you have a lean air-fuel mixture. (P0172, P0175) means you have a rich air-fuel mixture.
  2. Engine Misfire Code (P0300-P0305): If you get any error codes between P0300 and P0305, the car’s ECU has detected that your car’s cylinders are misfiring and not functioning correctly. Issues with the spark plugs, faulty ignition system, or internal engine failure can trigger this.
  3. Evaporative System Codes (P0411, P0440, P0442, P0446, P0455): This failure code is activated when the EVAP system fails to contain the vapors from burned fuel or because of a leak of pressure in your gas tank caused by a loose gas cap which allows fuel vapor to escape into the atmosphere.
  4. Exhaust Gas Recirculation Code (P0401): The P0401 code means there is a problem with the engine exhaust gas recirculation (EGR) valve not recirculating enough exhaust gases into the intake manifold.
  5. Catalytic Converter Code (P0420, P0430): The catalytic converters change toxic gases and pollutants into less harmful pollutants. The P0420 or P0430 indicates that the ECU detects performance below the threshold from the catalytic converter.

Also read: Whats an EGR Delete? (Pros & Cons)

Conclusion

The check engine light is an important feature in any car. Your car regularly runs tests to make sure everything is functioning properly. If the light comes on, it means your car failed the test two times in a row, and there’s an issue that needs to be addressed.

So Can a Check Engine Light Turn off by Itself? Yes, it can. If the car’s diagnostic system passes three times on the same test, it failed earlier – The light will turn off. However, diagnosing your vehicle with an OBD scanner for trouble codes is still a good idea.

I hope you found this article helpful. Happy driving!

FAQ

How Long Does It Take For a Check Engine Light to Go off?

It can take anywhere from a few days to a couple of weeks for a check engine light to turn off automatically. However, if the problem persists, you should bring your car back to the mechanic to check it out.

What Does It Mean If My Check Engine Light Goes on and off?

It often means you are dealing with a minor issue, but it shouldn’t be overlooked. Some of the problems that may cause your check engine light to go on and off are a loose gas cap, a failing oxygen sensor, bad spark plugs, bad mass airflow sensor.

SOURCES

https://www.noregon.com/what-is-obd/

https://www.edmunds.com/car-maintenance/what-your-check-engine-light-is-telling-you.html

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