In most cases, the check engine light comes on for a reason. However, there are also some times in which the check engine light won’t seem to turn off, even after you’ve tried to do so after attending to whichever issue caused it to come on in the first place.
Oftentimes, this could be because the vehicle’s computers haven’t had time to reset. Maybe you just had an issue fixed, and you expect the light to come back off as soon as you get your newly repaired vehicle back from the shop, but it doesn’t always work that way.
Any way you look at it, an illuminated or flashing check engine light should never be ignored. It can always be turned off, though. And sometimes, there really is no issue with your vehicle when it’s on.
That’s just the way it is with cars, and you can never really know what’s what until you know what you should look for.
The key here is knowing what the actual issue is. You can do that by using an OBD-II scanner to diagnose the problem.
After you’ve gone through all of that, if you really need to reset the check engine light, you can – and we’ll be letting you in on all the steps involved in doing that in this article.
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Why Would You Need to Reset the Check Engine Light?
Most of the time, it isn’t recommended to do this, especially if you don’t know what is causing the issue.
Other times, it feels like you absolutely need to do it, because it’s more like getting rid of an annoying mosquito that keeps buzzing around your head.
Vehicles’ electronic control units are very advanced. Almost every time, the check engine light will disappear on its own if a detected problem has been resolved, so resetting it is ill-advised in almost every scenario.
Despite that, there are a few situations in which you might want to perform this task. These situations include:
The Vehicle’s ECU Has Not Had Time to Reset Itself
A vehicle’s ECU often runs in a circuit, constantly monitoring sensors and systems to make the adjustments necessary to keep them running optimally.
When something abnormal is encountered, the ECU will try to correct the issue. If the issue isn’t able to be corrected, the check engine light will come on.
Because there are thousands of sensors and information points that your vehicle’s ECU handles, it might take a little while to figure out that there isn’t a problem after the issue has been fixed.
Every vehicle is slightly different, and older vehicles aren’t as sophisticated as the most modern ones. ECU cycles could take up to a few weeks to fully recognize when a problem is no longer there, depending on the vehicle.
The Vehicle Could Fail Safety or Emissions Testing
Each state has different requirements for vehicles to pass or fail a safety inspection. Some states also have emissions tests in addition to a state safety inspections.
For those states which have emissions tests, some will automatically fail your vehicle if the check engine light is on.
If you just fixed what’s been causing it to be constantly on, and you have a state safety or emission inspection coming up, you might need to do this to pass inspection.
You Know There Isn’t Actually a Problem
You have fixed your vehicle, and you should expect your check engine light to go off.
If it doesn’t, you may want to consider resetting it so that any more problems that might occur aren’t overlooked, especially if your vehicle takes a long time running through ECU cycles.
It Is Annoying
Probably the worst reason to want to do this is that it can be annoying.
Resetting it for the sole reason that it is annoying is almost always a bad idea. If the light is on, this means that there is a problem, even if it is a minor one.
Fixing an issue and then having the check engine light still illuminate can be even more annoying than having the light on in the first place, but this is a much better and more justifiable reason.
How Do You Reset the Check Engine Light?
There are several ways you can go about doing this.
Most are very easy to do, but some are not recommended as they can cause other secondary issues.
Here are several methods you can follow:
Fix the Issue Causing the Light to Illuminate
This should not come as a shock to anybody, but the best way to go about doing this is to fix the issue that is causing it to come on in the first place.
Every vehicle since 1996 is equipped with OBD-II, a universally mandated on-board diagnostics system that can be read by an OBD-II scanner.
This will help you or a mechanic diagnose and fix an issue which causes the check engine light to illuminate.
Just Wait for a Little Bit
For some vehicles, the root of the problem can be addressed and fixed, and the light will go out. For others, the ECU will take some time to fully run through its cycle of checks, and could take days or weeks to clear fault codes.
As long as you know that an issue has been fixed, there should not be any problems with simply waiting for the check engine light to turn off on its own, whenever it’s ready to.
Driving your vehicle around as you normally do will allow all ECU cycles to complete themselves.
Turn the Ignition on and off Several Times
Turning your vehicle on and off several times in succession can also be a possible way to reset your check engine light.
This will only work on some vehicles, though, but it is a better method to try at first, before moving on to any of the other more tricky methods.
To complete this, turn your vehicle on for one or two seconds. After that, turn it off for another one or two seconds. Repeat this at least three times, and you may very well end up succeeding.
Disconnect the Battery, and Drain the Remaining Power in the System
Before disconnecting the battery, you must find it first. Battery locations vary between vehicles, though the most common place they tend to be in is under the hood.
You can disconnect the positive battery terminal, the negative battery terminal, or both battery terminals from the battery after you locate its position. You will need a wrench to unscrew the bolts holding the terminals onto the battery.
Make sure that the vehicle is off before you open the hood and disconnect any battery components.
It is also a good idea to turn on the vehicle’s headlights or hold the horn down for a minute after the battery is disconnected, to drain residual energy that might be in the capacitors.
Once everything has been disconnected and the remaining battery power has been drained, allow the vehicle to sit for up to 30 minutes. After that, reconnect the terminals, tighten them to the battery, and turn the ignition on.
Disconnecting the battery essentially erases the vehicle’s memory. Not only will doing this most likely reset the check engine light, but the radio, anti-theft control system, and other components will likely be reset as well.
Not every vehicle will behave this way, though. For example, some vehicles store fault codes in the ECU, and will continue to display an illuminated check engine light.
Clear the Fault Codes by Using an Obd II Scanner
The easiest, safest, and most common method to follow in modern vehicles is to clear the code or codes with an OBD-II scan tool.
To do this, plug in an OBD-II scan tool to the OBD port of your vehicle. Your owner’s manual should pinpoint its location, but in most cases, it will be located next to the fuse box between the steering wheel and driver’s door.
Once the scan tool is plugged in, turn the vehicle on. Once the vehicle has been turned on, you’ll need to turn the scan tool on, let it boot up, and press “scan.”
The tool will then read the error codes, display them, and you will have the option to clear some (or all) of the codes that have been read by the scan tool.
Be sure to make note of each code present after the scan is complete.
After you’re done with all of that, press “clear” to erase the codes or “enter” when asked if you are sure you want to clear the codes, and the check engine light should be successfully reset and no longer illuminated.
For more useful information that could come in very handy in your situation, watch this video.
What Tools Do You Need to Reset the Check Engine Light?
Resetting the check engine light will require a minimal number of tools.
As a matter of fact, you may not need any tools at all depending on your method of resetting the light, but you should still have some of these tools handy just in case your first attempts don’t work.
Gloves are useful when you do any kind of maintenance on a vehicle.
They can be especially helpful if you have to perform a hard reset and get to the battery under the hood.
Pliers or a Wrench
If you are planning on disconnecting the battery terminals, you will need a wrench or pliers to remove the bolts holding the terminals onto the battery.
OBD II Scanner
OBD-II scanners come in a variety of different prices, forms, and functions, all depending on what kind of work you plan on doing with them and just how advanced you need them to be.
You can buy them online or at an auto parts store from $20 to well over $1000 for professional grade OBD-II scanners.
They can connect to your vehicle’s OBD port via a cable, or they can be bought as Bluetooth devices with smartphone apps without cables.
Weights and sizes can also vary as well. Bluetooth scanners can be no larger than your OBD port, while large scanners can weigh over 10 pounds.
More sophisticated, higher-priced scanners will provide more details than less expensive models, and are most often only found in mechanic shops.
What Happens If the Check Engine Light Comes on After You Reset It?
If you have taken all the necessary steps there are to take, and it remains on or comes back on after turning off for a short while, you will most likely need to seek a mechanic’s advice in such a case.
Most of the times, this means that the vehicle is continuing to find a fault in one of its systems, and a potentially serious problem is recurring.
Just because you reset the check engine light doesn’t mean that a problem has gone away.
What Should You Do If You Can’t or Don’t Want to Reset the Check Engine Light Yourself?
Mechanic shops and some auto parts stores will often do a reset for you for free.
Even though OBD-II scanners are available for everyone, many people don’t have them, and others who can afford them aren’t confident in their abilities to use them properly.
If you don’t want to go through the hassle of doing this all by yourself, then have your trusted mechanic do it for you.
Most likely, they will clear the code with the scan tools they have at their shop.
Are There Any Other Tips I Should Know About?
Before trying to reset the check engine light all on your own, make sure that the issue which caused the light to come on in the first place has actually been fixed.
Remember that getting it to turn off won’t solve an underlying issue that still exists, one which could be causing some serious damage to your engine.
Also, the battery disconnecting method has been around for a while, and is sometimes called a “hard reset.” It is a last resort measure, as important engine system and emissions data can be lost from lack of electrical power to the ECU.
This loss of data could be problematic if your state requires emission testing, and it may cause your vehicle to fail inspection.
Be sure to inspect your vehicle for minor issues before trying to reset the check engine light with any procedures mentioned above.
Oftentimes, this problem is caused by minor issues like a loose gas cap, loose wire or plug, or a disconnected sensor.
So, before you check whether any of the more serious problems are going on, be sure to check for the small stuff that you might otherwise wrongfully dismiss!
As you’ve seen for yourself by now, resetting your check engine light is not really difficult, but it should always be done with great discretion.
A constantly illuminated light is annoying, but that alone isn’t a good reason to try and get rid of it, especially if there is known issue going on.
After all, it’s there for a reason, and should not be neglected when it comes on.
The best way to reset the check engine light is to fix the underlying problem that’s causing it to come on in the first place.
Using an OBD-II reader is the most popular, easiest, and safest way to reset the light. On the other hand, doing a hard reset by disconnecting the vehicle’s battery is the most involved and riskiest way to try to solve this, and should be avoided unless absolutely necessary as a last resort.
Under most normal circumstances, you should never have to reset your check engine light on your own, anyways.
You see, vehicles are so advanced today that simply fixing the issue will cause the light to turn off immediately on its own. With that being said, this doesn’t always happen (even though it almost always should), and it’s still good to know how to reset the check engine light if necessary.