Once the Check Engine Light shows up, you know there’s something you must address. The onboard diagnostics (OBD) system analyzes the various car components to ensure everything is working correctly.
If there’s a fault, you will see the warning message appear on your dashboard or information display. That’s when you need to know how to reset the Check Engine Light.
In this guide, we give you some suggestions and discuss why it’s important to fix the underlying problem first. We also touch on what to do if the engine light comes back on and give you some answers to questions that have been bothering you.
Understanding the Check Engine Light System
What is the Check Engine Light?
The check engine light, officially known as the Malfunction Indicator Lamp (MIL), is a federally mandated warning system that has been required on all vehicles sold in the United States since 1996.
This amber-colored warning light is your vehicle’s primary method of communicating emissions and engine-related problems that could affect performance, fuel economy, or environmental compliance.
The light is part of your vehicle’s On-Board Diagnostics (OBD) system, a sophisticated computer network that continuously monitors dozens of engine and emissions system components.
When the system detects a malfunction that could affect emissions or engine performance, it illuminates the check engine light and stores a diagnostic trouble code (DTC) in the vehicle’s computer memory.
How the System Works?
Your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) serves as the brain of the diagnostic system. This computer continuously monitors sensors throughout your engine and emissions system, including:
- Oxygen sensors that monitor exhaust gas composition
- Mass airflow sensors that measure incoming air
- Throttle position sensors that track accelerator input
- Catalytic converter efficiency monitors
- Evaporative emissions system components
- Engine temperature and pressure sensors
The system runs continuous monitoring for critical safety and emissions functions, and non-continuous monitoring during specific driving conditions called “drive cycles.”
When a problem is detected, the ECM generates a specific diagnostic trouble code and illuminates the check engine light to alert the driver.
What Causes Engine Check Light On?
Before solving a problem, you must know where the fault is coming from. This is also true with vehicles. Like I stated, the engine check light helps notify the driver of electrical or mechanical faults within the vehicle.
In some cases, it could be an error from your engine. Before carrying out other checks, ensure there are no slipups in your engine.
If your engine is okay, then you might want to have other components checked. Possible causes of engine check light on are:
#1. Faulty Oxygen Sensor.
The oxygen sensor helps burn up gas in your car’s engine. The amount of oxygen in your exhaust that is left unburnt is measured by this component. When this component is faulty, your car will burn more fuel.
Excessive fuel burning will lead to the damage of your car’s spark plugs and catalytic converter.
So long the oxygen sensor isn’t working as it should, your engine check light will illuminate. You may need to visit an expert mechanic to have it replaced. Else, you won’t pass your car’s emission test.
#2. Faulty Catalytic Converter.
Aside from a bad 02 sensor, another thing that can damage your cat is poor vehicle maintenance, such as irregular oil changes and running short distances. This can cause the catalyst to get clogged, then, trigger the engine warning light to come on.
#3. Vacuum Leakage.
One function of the vacuum system is to reduce toxic emissions. Once there is a leak, your car would spurt or settle at an uncommon high PRM. The leak is usually caused by damaged fittings, loose connections, or the dryness of the vacuum hose.
#4. Loosed Gas Cap.
If your gas cap is loosed, it could be due to a mistake from your end. A loose gas cap will disrupt the system that delivers fuel to your car because it has failed to keep your car under the right pressure. This will result in fuel loss and cause your CEL to come one.
It may be that you forgot to replace the gas cap or tighten it properly after fueling with gasoline. This can happen to anyone, especially when in haste to go out.
But I will advise that you should be cautious of this cap. Gasoline is highly explosive, so you don’t want to drive with the gas cap out of place. Most times, if the gas cap is the problem, the CEL will disappear after you fill and tighten the cap properly.
So ensure you replace or tighten the gas cap properly after fueling with gasoline. If the gas cap is faulty, please have it replaced.
#5. Mass Airflow Sensor Failure.
This component measures the quantity of air that enters your car and enables your car to adjust to changes in height. When it is faulty, you will experience tough idling, reduction in gas mileage, and unexpected change in your throttle pedal.
#6. Faulty Thermostat.
The thermostat controls the flow of coolant to your engine. When it is bad, it causes your CEL to come on.
#7. Defective Alarm Systems.
Car alarms are made to prevent car thefts. But if they don’t work appropriately, it will cause your CEL to turn on. Not all alarms can work effectively, so ensure you get a quality one that can prevent theft.
Stay away from cheap alarms. You don’t want an alarm that will malfunction and cause your CEL to illuminate or damage other vehicle components.
#8. Faulty Ignition Coil And Spark Plugs.
Your vehicle’s spark plug gets power from the ignition coil, which makes them radiates sparks. The spark, in turn, burns the fuel and air mixture in your car’s cylinder.
When this coil is faulty, the spark plugs won’t get enough electricity to carry out their function. Thus, causing the engine check light to come on.
In other cases, if the coil is good, but the spark plugs are old or worn, your engine will misfire and cause the CEL to light. Therefore, ensure you replace bad engine coils or old/worn-out spark plugs.
#9. Dead Battery.
Your battery should last at least 5 to 7 years. If it has expired, it may not charge well and cause your engine light to come on.
Again, depending on how you use it, it might get worn out before then. So if it doesn’t charge and also gives you issues, then you will need to replace it.
How To Reset Engine Check Light?
#1. Use an OBD2 Scanner.
With your compatible OBD2 scanner, you can reset the Check Engine Light in a matter of seconds. If you don’t have one, we recommend checking out some of the best OBD2 scanners to purchase because this is going to be the easiest method.
- To turn off the codes with your scanner.
- Connect the scanner to your car’s OBD2 connector. It’s found near the floor under the steering wheel on the left side.
- Switch the ignition to the ON position.
- Once a connection is established, press the READ button on the scanner. All of the stored diagnostic trouble codes (DTCs) will show up.
- Erase any errors that you have repaired from the scanner by pushing the ERASE/CLEAR button.
After that is complete, switch the ignition back off and on again to see if the light has disappeared. You can also plug the scanner back in to make sure all of the codes are gone. If the codes come right back on, you know that you haven’t resolved the problem yet.
#2. Battery Disconnection Technique.
How do you reset the Check Engine Light without a scan tool? The easiest option is to disconnect the battery. This method requires a minimal amount of time and it will reset the engine control unit in most of today’s vehicles.
Before you disconnect the power, keep in mind that without the battery, you may lose some of your car memory. For example, you may need to set up the stereo preset, seat memory and clock again. Here are some steps to follow:
- Remove the negative battery terminal.
- Drain the electricity from the car’s capacitor by pushing down on the car horn for 20-30 seconds. You could also turn on the lights to drain the battery.
- After the power is drained, walk away for about 15 minutes.
- Reconnect the battery terminal and make sure it is secure.
- Start the car.
If this method doesn’t remove the Check Engine Light, either you haven’t fixed the problem or you need to attempt one of the other options.
#3. Cycling The Ignition On And Off.
There’s another way to perform a hard reset without a compatible code scanner. By simply turning the ignition on and off several times, you may be able to get the warning light to go away.
Every automaker has a different set of steps for this method, so you may need to do a little more research.
Typically, you will turn the ignition on and off several times, with a few seconds between each switch. After that, the Check Engine Light may be gone.
#4. Drive Your Car And Let The Light Go Off By Itself.
If you have fixed the underlying issue, you may be able to get the Check Engine Light all by itself. Once you do a little driving, the self-checks should show the computer that everything is now fine. That triggers the light to turn back off.
However, this process could take some time. Depending on what is wrong, it could take several days before the fix registers. As an example, if you repair a problem with the oxygen sensor, the code won’t reset until the ECU determines that the fault is fixed.
If your Check Engine Light remains on even after driving for three days, you may not have fixed the issue. If you aren’t sure what to do next, you can try the other methods listed or you can take your vehicle to a mechanic.
#5. Pulling the Fuse.
There’s also the option to pull the fuse for the Engine Control Unit. This may cause it to reset, thereby wiping out the codes. However, this repair method tends to only work on older cars.
If you aren’t sure where the fuse is located, take a look in your factory service manual. Because it only takes a few seconds to pull a fuse, it’s worth trying.
What If The Check Engine Light Returns?
In the worse scenarios, the check engine light may come back within a few days or weeks, which may signal a major complication.
If it keeps happening, despite the resetting procedures, you should take the car to a service center and have it diagnoses by a professional mechanic.
In case you want to self-inspect the relighted engine light, you can follow some notices below.
#1. Read the error codes again.
Use an OBD-II scanner to retrieve the error codes. Note down the specific codes, as they provide crucial clues about the nature of the problem.
If the codes are the same as before, it confirms the original issue wasn’t fixed. New codes might indicate a different problem or a related issue.
#2. Research the codes.
Look up the meaning of the error codes online or in a repair manual. This will give you a better understanding of the potential causes and help you narrow down the possible culprits.
#3. Inspect for obvious issues.
Depending on the error codes, you might be able to check for some obvious problems yourself.
For example, a loose gas cap can trigger certain emissions-related codes. Check for vacuum leaks, damaged wiring, or other visible issues that might be related to the codes.
#4. Consider recent repairs or modifications.
If the check engine light returned shortly after a repair or modification, it’s possible that the repair wasn’t performed correctly or the modification caused unintended consequences. Double-check the work or consult with the mechanic who performed the repair.
#5. Don’t ignore the light.
Continuing to drive with the check engine light on can potentially worsen the problem and lead to more extensive and expensive repairs. Address the issue promptly to prevent further damage.
FAQs.
Q: How Do I Clear My Check Engine Light Without A Scanner?
First, ensure you have fixed the problem. The scanner is the most efficient and modern way of resetting check engine lights.
But a high-end scanner is quite expensive and will range from $100 to about a thousand dollars. In reality, not everyone can afford it. If you can borrow from a friend or hire one, fine. But in its absence, other methods can be employed.
The following highlights how to clear check engine lights without a scanner.
- The battery disconnection method.
- Turn off and on your ignition.
- Letting it go by itself by running your cars in cycles.
- Or you can employ the pulling of the fuse and putting back fuse method.
If you started reading from here, please scroll up, as I have already explained these methods listed here.
Q: Can You Reset Check Engine Light Without Disconnecting The Battery?
There are many methods you can use to reset CEL. So yes, you can reset your check engine light without disconnecting the battery.
You can do it using a code reader or scanner. In some cases, the light will disappear itself after driving your car for a while. But remember, you must have fixed whatever problem is wrong with your car.
Q: How Long Does It Take For Check Engine Light To Reset?
After fixing the problems, it should take about 10 to 30 cycles before the light disappears. Remember, a complete cycle is turning on your engine, drive until it’s warm, then, put it off again.
Q: Why Is My Check Engine Light Off, But Code Still There?
If the light is off, but the code still appears, it may be due to several reasons. The fault that caused the error code occurred many times to turn on the light.
This, in most cases, means the problem is not critical, so the code is just stored. In other cases, it could be bad electrical connections or wiring issues. Faulty sensors or stuck valves can also cause it.
In this case, using a scanner or code reader to detect the actual problem will be the best option. The scanner will tell you the problem and things you need to get fixed. But if you can not decode the fault code and fix the problem, reach out to a mechanic.
Q: How Do I Permanently Delete Engine Codes?
To permanently delete engine codes, you will need an OBD 2 scanner or code reader. Would you mind looking up to see the steps on how to erase engine codes using the scanner?
Please, do not clear trouble codes without deducing where the error codes came from and fixing them.
Final Thoughts
By now, you must have learned different methods of how to reset the check engine light. One of which is the use of an OBD 2 scanner or code reader. Not only does it reset the check light, but it can also detect what the problem is.
For the other methods, know that several faults in vehicles can trigger the check engine light to come on. So it would help if you first diagnosed what the issue is, then fixed it before you reset the CEL. If you do not reset this light, you will fail your car’s emission test.
We’ve tried to show you everything simply. All these DIY procedures are pretty easy to perform and deal with.
However, things may go wrong sometimes. If you’ve gone through all these steps and you couldn’t solve the problem still, you need to seek help from an expert automotive mechanic.