That dreaded check engine light happens to all of us, even with the most reliable cars. Of course, a check engine light usually means there’s something wrong with your car, but what if you’ve fixed it and it still won’t go away? We’re here to help you understand what it is, and how to reset a check engine light.
- Understanding the CEL
- How to Reset a CEL
- What if the CEL Returns?
- Common Causes of a CEL
Check Engine Light
It’s important to understand what a check engine light is and what it means. Basically, your car has a lot of electronics on it, one of which is an OBD system or an On-Board Diagnostics system. This system is responsible for detecting if there’s something electronically or mechanically wrong with your car and then warning you.
In some cars, the check engine light can either flash or be lit continuously. If the check engine light flashes, then it usually means something serious and it’s recommended to stop your car and tow it to prevent further damage. Meanwhile, a check engine light that is lit continuously usually means it’s not too serious and you can keep driving.
In any case, after you’ve fixed your car, your car’s OBD will run checks and the check engine light will go away on its own. However, sometimes the computer needs your help to tell it that the problem has been fixed.
If it’s the latter, then you will need to manually reset the check engine light. Otherwise, your car won’t be able to tell you if something else goes wrong in the future.
Reset Check Engine Light
If you’ve fixed your car but the check engine light is still there, there are four methods to get rid of it. Some methods will simply require you to drive for a bit, others will require tools. Here are the four methods you can try to reset a check engine light:
1. Take A Drive
This is the simplest method of all. Once you’ve fixed the problem in your car, take it for a drive as you normally would. As mentioned previously, your OBD will run checks regularly. Then, if it recognizes that you’ve fixed the issue, it will reset the check engine light on its own.
However, this method can be time-consuming as it can take some miles for the OBD to realize it. If it still won’t go away after many miles, you have to check again on whether or not the issue has been fixed. If you’re sure that it’s been fixed, then you’ll have to try other methods to get rid of that check engine light.
2. Have You Tried Turning It Off And On Again
Tech support often suggests this whenever something’s wrong with our laptop or internet modem, and yes, we’re suggesting you do the same for your car. No, for real, we’re not joking. We know this normally never works for your laptop, but try doing this three times with your car and it could help to reset the check engine light.
For some cars, this method will help reset its computer and gets rid of the error codes that caused the check engine light. Simply turn on your car for about a second, and then turn it off again for about a second. Do this in succession three times, and then take a quick drive in your car and see if it gets rid of the check engine light.
3. Disconnect And Reconnect The Battery To Reset Check Engine Light
If turning it off and on again doesn’t work, then it’s time to try disconnecting and reconnecting the battery. Doing this will do a hard reset on your ECM (Engine Control Module) or sometimes called ECU, forcing your cars’ computer to run a diagnostic check when reconnected. Kind of like forcing a reset on your phone when the screen freezes.
Working on a battery can be dangerous since it’s where your car’s whole electricity comes from. If you have any intention of doing this method, you should follow these safety measures first:
Cautions Before You Disconnect A Car Battery
- Remove any accessories such as metal jewelry, rings, and watches. These are excellent conductors for electricity and could trigger an electric shock. Best leave them off your body.
- Keep everything dry, as the slightest amount of water that touches the battery can spell disaster. This goes without saying, you should work indoors if it’s raining.
- Turn off your car before you touch the battery.
- Work in a well-ventilated space, as battery contains acid and it’s likely to emit harmful gases.
- Check for signs of corrosion. If there’s a widespread greenish-white powder, then be extra careful or even hire a professional mechanic instead, just to be safe.
How To Hard Reset Your Engine Control Module
Once you’ve followed the safety measures above, then you can start working on the battery and do this method. The steps are as follows:
- Open the car’s hood.
- Disconnect the Negative (-) power cable, and leave it for 15 minutes.
- Insert your key into the ignition and turn it to the “ON” position three times.
- Reconnect the Negative (-) power cable and turn on the car’s ignition.
- Wait one minute to see if the check engine light is gone.
There are several ways of doing this method. Sometimes, simply leaving the battery disconnected for a while and draining the remaining electricity in the car could do the trick. You can watch the video below if you need help:
Keep in mind that this particular method might also reset some other things in your cars such as your clock and radio settings. If this method still hasn’t worked, we recommend checking your car once again. It’s possible that the issue that caused the check engine light in the first place hasn’t truly been resolved. However, if you’re sure it’s been fixed correctly, you can try the last method:
4. Use An OBD Scanner To Reset Check Engine Light
An OBD scanner helps to identify the specific problem in a car by scanning the car’s computer for error codes. This means you can also use it to clear that error code and reset the check engine light. There are several OBD scanner brands available, with varying complexity and prices. However, before you buy an OBD scanner, here are some things we’d like you to note:
Does Your Car Use OBD-1 Or OBD-2?
Cars made before ’95 have an OBD-1 scanner, while cars made in ’96 and onwards usually come with OBD-2. We won’t bore you with the details, but if your car has an OBD-2 then it should work universally with any scanner. Meanwhile, the older OBD-1 scanner is usually manufacturer specified and you need a specific device or software that was issued by the manufacturer.
If you’re planning to purchase an OBD scanner, be sure to recheck which OBD your car comes with so that you’ll buy the correct one. You can easily check this online. If your car has an OBD-2, there are several types of scanners you can find online, which are:
Bluetooth OBD Scanners
These are the smallest kind of OBD scanners. The scanner is a small box that you have to plug into the OBD port, and then it connects via Bluetooth to your phone. Of course, you need an app on your phone to see the diagnostics. The app itself can either be free (usually they’ll let you know which app to download when you purchase the scanner) or you’d have to pay.
If you’re interested in using a Bluetooth OBD scanner, the BlueDriver Pro Scan Tool is often recommended.
USB OBD Scanners
As the name suggests, a USB OBD scanner connects via USB, and you need to have a laptop to connect with the OBD. When you purchase a USB OBD scanner you will simply get a cable that connects the OBD port to a USB port. Then, once connected you’ll have to install their software on your laptop.
The software either comes in a CD which they include in the box or you’d have to download it. It can either be free or paid, an example of this OBD scanner is the ScanTool OBDLink SX. This type of OBD scanner is often used by professional mechanics, sometimes used to tune cars as well.
Stand-Alone OBD Scanners
This is the most common type of OBD scanners. As the picture above shows, it’s simply an OBD cable connected to a stand-alone device. Because of the simplicity, you’ll find this commonly used in most repair shops and DIY enthusiasts. This type of OBD scanner varies in complexity, there are more complex ones that can show more data when reading the OBD system. However, it can cost thousands of dollars and is unnecessary if you’re just doing a quick scan.
How To Use An OBD Scanner
If you don’t feel like purchasing an OBD scanner, you can borrow them should you know anyone who owns one. In any case, once you got the scanner, here’s how to use it:
- Plug the reader into the car’s OBD port. This port is often located underneath the dashboard area, either above your pedals or knee. Keep in mind that some cars might have their port hidden out of sight. Check your owner’s manual or online to see where it’s located in your car.
- Once plugged in, turn on the OBD scanner. It should immediately scan the car. However, some scanners might require you to input additional information such as make, model year, VIN number, etc.
- It will then display the error codes it has found. A more complicated scanner might also display a description of what’s wrong with the car, but if you have a simpler scanner then it’s recommended to take note of the codes displayed. This way, you can cross-check them with the owner’s manual later on.
- Once done, find the option to erase the codes. This will delete the error codes and should get rid of your check engine light.
If you need visual instructions, you can watch the video below on how to use an OBD scanner:
After doing this, your error codes will be gone and it’s usually a surefire way to get rid of the check engine light.
Why Is My Check Engine Light On
As mentioned previously, the first three methods might not work in getting rid of the check engine light. But the OBD scanner is usually a sure way to get rid of it. However, the check engine light could return and it’s usually because of one of two things: either the original problem hasn’t been truly resolved, or a new problem has occurred.
This is why if you’re trying to fix your car yourself, it would be wise to write down the codes that appeared. This way, when you try scanning your car again, you can crosscheck whether the codes that appear are different from the previous OBD scan. If the codes are different, then there’s a new problem with your car.
In any case, if the check engine light persists and you feel it’s too tiresome to deal with, we recommend taking your car to a professional mechanic to get a full diagnostics. A simple checkup might be quite costly at around $75, but it saves you the time from having to check it yourself.
Once diagnosed, you can then decide whether to do the repairs yourself to save some labor costs, or trust your mechanic or repair shop to deal with it.
What Causes Check Engine Light To Come On
If your check engine light returns or you’re experiencing it for the first time, there are several simple things you can check first, such as checking your gas cap and spark plugs. Afterward, it could go away on its own. However, if the check engine light persists and you’re wondering what it might be, there’s a list of common things that might be wrong with your car.
According to CarMD, a car telematics company, here are the 10 most common causes of a check engine light according to their research:
1. Faulty Spark Plugs
A spark plug is responsible for combusting the fuel and air mixture in the engine’s combustion chamber. Because of this, it’s essential for the engine to run smoothly. Over time they will wear out and lose their spark and efficiency, in which case you will need to replace them. Spark plugs in most normal cars should cost no more than $10 each, sometimes cheaper.
2. Replace Oxygen Sensor
The oxygen sensor or O2 sensor is also a common cause for the check engine light. This sensor is responsible for determining the amount of oxygen in a car’s exhaust. While it usually only costs a few hundred dollars to repair, ignoring it can lead to more severe issues. For example, a faulty O2 sensor can reduce your car’s fuel efficiency by up to 40%.
If your oxygen sensor is faulty, the average price of replacing it is around $240.
3. Bad Catalytic Converter
A catalytic converter is used to control your car’s emissions and reduce toxic gases from your engine. It can be quite costly to fix this one, around $1,300 according to CarMD. One of the most common causes for this is ignoring a faulty or bad spark plug, which is why it would be wise to replace your spark plug should you need to.
Ignoring a bad catalytic converter (as is the case with the 2011 Equinox catalytic converter recall) can cause loss of performance and fuel efficiency. Not to mention the car will emit excessive amounts of toxic gases as you drive.
4. Possible Loose Gas Cap Or Replace As Necessary
A loose gas cap can be a common cause for a check engine light, and you can simply tighten it up to get rid of the light. However, your gas cap may wear out over time and it won’t close as tight as it used to. In which case you will need to replace them, and the price depends on your car’s make and model. The average price is usually around $25.
5. Faulty Ignition Coil
Remember the spark plug? Well, the ignition coil is what’s responsible for giving your spark plug the electricity it needs to make the spark. Therefore, an ignition coil is also crucial for your engine to run properly. Ignition coils may fail overtime or fail due to high temperatures. Whatever the case, you don’t want a faulty ignition coil, as you will struggle to even start the car in the morning.
The average cost of replacing an ignition coil is around $215. If left unfixed, it can lead to more issues such as a bad catalytic converter, which will cost even more money.
6. Replace Evaporative Emission Purge Control Valve
An Evaporative Emission Control System or EVAP is used to prevent gasoline vapors from escaping the fuel tank and system. There may be a leak sometimes in the EVAP system, and it can cause loss of performance, fuel economy, and even trouble in starting the engine. On average, the control valve for an EVAP system usually costs $150 to replace.
7. Mass Airflow Replacement Is Needed
A mass airflow sensor or MAF is responsible for determining how much fuel to put in the engine, depending on the amount of air the engine is getting. A faulty MAF sensor will cause the engine to put the wrong amount of fuel, leading to an incorrect air-to-fuel mixture. This will affect performance, fuel efficiency, and can lead to further engine damage if left unserviced.
A mass airflow sensor can be quite pricey to replace, which is around $340 on average.
8. Evaporative Emissions Purge Solenoid Replacement Needed
This feature is part of the EVAP system, and it helps to control how much fuel vapor escapes into the atmosphere from your vehicle. You will need around $150 to replace a faulty solenoid.
9. Faulty Fuel Injector
A fuel injector is responsible for injecting the right amount of fuel into your engine’s combustion chamber. A faulty fuel injector may inject the wrong amount of fuel, causing misfires while driving and leading to further damage to other components. Prices for a fuel injector vary between cars, but according to CarMD, the average cost is about $450.
10. Replace Thermostat
A thermostat is responsible for regulating your car’s engine temperature. A failing thermostat can cause the car to overheat even under normal driving conditions. You can typically avoid this by changing your car’s coolant regularly (as recommended by the manufacturer is fine). The cost to replace a thermostat varies between car make and models, but on average it’s around $240.
Keep in mind that these are only the top 10 causes, so your check engine light may be indicating something else entirely. That being said, now you know what to expect when you see a check engine light on your dashboard.
Check Engine Light Facts: Resetting and Troubleshooting
- The check engine light indicates an electrical or mechanical problem with your vehicle and can cause issues with emissions testing and alert you to future problems.
- It’s important to ensure the light isn’t on due to an ongoing problem before attempting to reset it.
- Four methods for resetting the light include driving and waiting for it to turn off on its own, turning the engine on and off three times, disconnecting and reconnecting the battery, and using an OBD code reader.
- An OBD code reader is the most effective method for resetting the light and analyzing and clearing engine codes.
- The check engine light can turn off by itself in some cases, but intermittent turning on and off could indicate multiple potential culprits, such as a loose gas cap or faulty valves.
- The check engine light may not turn off automatically after repair, and an OBD reader may be needed to reset it.
- A code reader can manually clear fault codes or provide an error code that explains why the light is on.
- If you need to reset the light without an OBD reader, it may be more difficult, and there could be a mechanical issue with the vehicle.
- If the check engine light comes on after replacing fuses, it could be due to incorrect fuse values, a bad fuse, or a coincidence of another system malfunctioning.
- If the check engine light continues to come on after attempting to fix it, connecting the vehicle’s computer to an OBD2 reader can help determine the issue.
How To Reset A Check Engine Light: In Conclusion…
If your check engine light comes on, be sure to resolve the issue immediately. It’s never wise to ignore a warning that your car is telling you. The system is there to help you keep your car in top condition and running perfectly and safely. Ignoring a check engine light might lead to more serious problems in the future, and potentially endanger you while driving.
Do not reset your check engine light unless you’ve fixed the issue. Once fixed, then you can try one of the methods above to get rid of the light. If you have access to an OBD scanner, then it’s the surefire way to get rid of the check engine light. However, any of the other previously mentioned methods should work just fine as well. Provided you’ve already fixed the issue.
If the check engine light persists, there might be something else wrong with your car or the issue hasn’t been fixed correctly. In which case, you can try to diagnose it yourself. However, visiting your trusted mechanic or repair shop is also a good idea since they probably know how to handle it better and help save you some time.
FAQs On How To Reset A Check Engine Light
If you’re still curious about how to reset a check engine light, our FAQs here might explain more…
What Does Check Engine Light Mean
A check engine light is sometimes referred to as the malfunction indicator lamp. When your check engine light comes on, it means that your car’s onboard diagnostics have found an error somewhere in the vehicle. Oftentimes, it indicates that something mechanical, electrical, or electronic has gone wrong in your car. It’s able to do this, as your car’s onboard diagnostics constantly collect data from countless sensors throughout your car. These sensors can check how the engine’s doing, or if your car’s emissions systems are working properly. If any of these sensors find that a particular component isn’t working right or has gone out of spec, it’ll alert the onboard diagnostics (OBD) and store an error code for analysis. To let you know there’s an issue, the OBD will also light up the check engine light as a warning to the driver.
What Does Service Engine Soon Mean
Alongside the check engine light, some cars might even show you a warning message that reads, ‘service engine soon’. Unlike the check engine light, the service engine soon light isn’t as serious. Most of the time, automakers would program the service engine soon light and message to come on if something minor has gone wrong with your car. Where a check engine light appears for larger and more consequential problems, the service engine soon light is something that you can more or less ignore for the time being. On the other hand, some automakers program the service engine soon light as an early reminder to get your car serviced. This would automatically come on if your scheduled service is due, like an oil change or a spark plug replacement.
What To Do When Check Engine Light Comes On
If you’re seeing the check engine light turning on, it’s best to act fast. There are occasions where the check engine light appears for smaller or trivial issues, such as if your car has a loose gas cap. But most of the time, seeing a check engine light is an indicator that something bad has gone wrong with your car. Therefore, if you see the check engine light, you should immediately drive to the nearest workshop to have it checked. The seriousness of the underlying problems would depend on the state of the check engine light. If it’s just lit up in orange or yellow, then it might not necessarily be as serious. However, if the light is lit up in red or if it’s flashing, it’s a sign that a major problem has appeared and needs fixing right away.
How To Clear Check Engine Light
If you see a check engine light on your dash, there are several ways to clear it. In some cases, just driving your car for a little while is enough for the onboard diagnostics to complete its self-checks. If all is well, the check engine light would turn off on itself. Otherwise, turning the ignition off and on again might sometimes clear it, too. If that doesn’t work, try disconnecting and reconnecting the battery, which would reset your car’s computer. That might help to clear the check engine light. If all of the above doesn’t work, you might have to perform a hard reset by connecting an OBD diagnostics tool to your car. Then, use the scanner tool to forcefully clear and reset any check engine lights. If the light comes back, it typically means that a serious issue needs fixing.
How Long To Drive After Reset Computer To Pass Emission Test
One of the factors for passing an emissions test is checking your car’s onboard computer. If you’ve just recently reset your car’s computer, you will need to give it some time for the onboard diagnostics to run all its checks and self-tests. After all, resetting the computer will wipe away previous checks, necessitating that you start anew. This can be done by simply driving your car for a little while. All that driving will give the onboard computer the time and data it needs to pass all of its onboard tests and checks. But how long do you need to drive? This varies from one car to another. In general, though, most cars need at least 50 miles worth of driving before they can properly complete all their onboard checks. Granted, there are cars that need at least 100 miles of driving.