Home Diagnosis and TroubleshootingDashboard Warning Lights What To Do When Check Engine Light Comes On: How To Fix It

What To Do When Check Engine Light Comes On: How To Fix It

by Jordan Harris
Check Engine Light Flashing

It can be frightening when the check engine light on your car starts to illuminate. But, what to do when check engine light comes on? Instead of stressing, think about doing the following to determine whether you need a serious repair or something as simple as a loose gas cap.

Your car uses chimes, icons, and messages to communicate with you even if it cannot speak. The orange, engine-shaped icon that is typically displayed in the instrument cluster is one that you should never disregard. When the onboard computer of the vehicle notices an issue, it switches on. This article will surely guide and help you to get through a check engine light.

Check Engine Light

It’s crucial not to ignore your check engine light if it illuminates while you are driving and to instead get in touch with a reputable vehicle repair company to find out what is triggering the signal. If the computer in your car detects a problem with how the car is operating, the light comes on.

Depending on the nature of the issue, the check engine light may illuminate and remain illuminated or it may flash. A light that flashes quickly typically signifies a power loss in the car or something even more critical. It is typically less serious when the light illuminates and remains on.

Colors are essential when it comes to dashboard lights. Simply said, green or blue lights indicate that a system is on or in use. Orange or yellow warning lights indicate that your car needs maintenance or repairs soon. The urgency of these warnings is lower than it would be if you had a red or flashing light.

A red light indicates that you need to move quickly! Some red dashboard lights are mechanical, while others are safety warnings (such as a seat belt reminder – if you ever needed seat belt repairs near me – or the engine overheating). When a mechanical red light comes, pull over as quickly as you can to investigate. If you continue to drive, your car will probably break down or get damaged.

Car Light Meanings

Not all of the icons on your dashboard correspond to warning lights. Some are related to mechanical problems, safety features (such as blind-spot monitoring and lane departure warnings), or vehicle functions (like lights and cruise control) (like low tire pressure and engine temperature warnings).

What To Do When Check Engine Light Comes On

Check Engine Light Codes

Four categories make up the diagnostic codes for check engine lights:

  • Powertrain (P)
  • Body (B)
  • Chassis (C)
  • Network Communications (U)

These codes are further separated into two major groups, which are as follows:

  • Enhanced or specific (1 is the second digit)
  • Generic or global (0 is the second digit)

Check Engine Light Blinking

Now that your car’s diagnostics have found a problem, what are you looking for now? Your dashboard will display a yellow check engine light, although the exact shape will depend on your vehicle. Some cars’ check engine lights just say “check engine” and nothing else, while others have an engine-shaped light that occasionally says “check.”

The issue may affect the light’s appearance, too. A flashing check engine light indicates a problem that must be fixed immediately, whereas a solid light suggests a less urgent problem. In some cases, if the issue is severe, a red light will also appear.

You should not overlook a flashing check engine light; in the long run, you may end up saving a ton of time and effort by acting swiftly to address the issue.

Check Engine Light On But Car Runs Fine

One of the most confusing signals your car sends is the check engine light since it can represent a number of different things. It can turn out to be a relatively little issue that is easily fixed, or it might be a very major one that could harm your engine.

The check engine light should not cause you to lose your cool while you are driving. Keep your cool and check to see whether the car is driving differently than usual. Even if everything appears to be in order, you should still take your vehicle to a mechanic right away to have the issue evaluated and corrected.

The easiest to fix is one of the most frequent causes of the check engine light. The dreaded light can quickly come on if you put your gas cap on improperly, loosely, or in a way that doesn’t establish a good seal. Frequently, all that is necessary is to inspect the cap and fix it if it is not properly attached.

If this is the case, you should be aware that even after you fix the cap, the light might not go out for some time. You can take a chance and try to drive during this period to see if the light turns off.

But it’s typically best if you or a professional first do a diagnostic test (more on diagnostics further down). This enables you to verify that by making these additional journeys, you aren’t aggravating a different problem that initially caused the indicator to come on.

Check Engine Light Diagnostic

You must first determine what is causing the issue. Fortunately, automotive technology has progressed significantly over the years, so we no longer have to deal with antiquated interfaces, thanks in part to EPA emission regulations. Modern cars use OBD2, a diagnostic technology that was far superior to OBD1 and enables us to scan our ECU to determine when something is amiss.

This was due to the fact that OBD1 was unable to identify any problems because it was only intended to control emissions and implement fuel injection. Since you had to personally examine each component, this significantly increased the amount of time needed to diagnose a problem.

Customers could more easily determine what was wrong with their vehicle thanks to the usage of OBD2. This is made possible by OBD2 scanners, which recognize the code that your car set off. These canners exist in numerous wired and wireless configurations, but they all do the same task. It is feasible to determine what code is being triggered with OBD2 scanners. After locating the fault code, you can move on to focus on a specific part of the issue.

What To Do When Check Engine Light Comes On

A flashing check engine light in this situation specifically indicates that one of your cylinders is misfiring. You shouldn’t drive your car without first determining the issue. Similar to how defective parts might result in a misfire, things like frayed cables or loose connections can also do so. If the problem is serious enough, you might need to locate an alternative.

Everyone’s lives have been made easier by the use of OBD2 system diagnostics, which can also help you avoid spending a ton of money by doing the work yourself. Make sure to get your vehicle evaluated right away if the light is on because there could be major issues.

Reasons For Check Engine Light

Your car uses chimes, icons, and messages to communicate with you even if it cannot speak. The orange, engine-shaped icon that is typically displayed in the instrument cluster is one that you should never disregard. When the onboard computer of the vehicle notices an issue, it switches on. The most typical issues that can trigger a check engine light are listed below.

What To Do When Check Engine Light Comes On, Causes #1: Oxygen Sensor Failure

The oxygen sensor, often known as an O2 sensor, gauges how much unburned oxygen is present in a car’s exhaust system. It transmits information to the car’s computer, which utilizes it to control how much gasoline and air enter the cylinders. Even if an O2 sensor needs to be replaced, an engine will still function, but it will use more fuel than usual.

A defective O2 sensor over time can harm parts like spark plugs and the catalytic converter. Additionally, it may make a car fail an emissions test. A good quality O2 sensor will typically cost you around $175. However, labor costs can differ greatly based on the make and model of the car and where you live.

What To Do When Check Engine Light Comes On, Causes #2: Catalytic Converter Failure

The exhaust system of a car includes the catalytic converter. It catalyzes carbon monoxide produced during combustion into less harmful carbon dioxide. It’s a reasonably straightforward component, and failure may frequently be avoided. That’s excellent news because, depending on the brand and model, a new one might cost anywhere from $200 to $600. Every modern gasoline-powered vehicle contains a catalytic converter.

What To Do When Check Engine Light Comes On

The catalytic converter in your car needs to be serviced on schedule in order to stay in good functioning order. If you live in the city and only travel short distances, take your vehicle occasionally on the highway to prevent the catalytic converter from being clogged. Additionally, as always, be alert for any odd noises or discolored smoke coming from the exhaust.

What To Do When Check Engine Light Comes On, Causes #3: Spark Plug/Ignition Coil Issues

Simply said, an ignition coil produces the electricity spark plugs required to ignite the mixture of gasoline and air in the cylinders. While many modern vehicles employ one coil per cylinder (commonly referred to as a coil pack), classic cars only have one coil.

You might have eight different coils if your vehicle has a V8 beneath the hood. The check engine light will very probably come on regardless of how many coils you have, but keep in mind that if your car runs on diesel, you don’t have any ignition coils or spark plugs.

Speaking of spark plugs, worn or clogged plugs can result in a number of problems, such as an engine that misfires and hesitation when accelerating hard. The same symptoms may be present with a worn coil, which can also result in an unexpected car shut-off.

While a coil typically costs between $50 and $60, a good spark plug is between $10 and $20. Additionally, it’s simpler than it seems to change your own spark plugs.

What To Do When Check Engine Light Comes On, Causes #4: Mass Airflow Sensor Failure

The amount of air entering the engine is monitored by the mass airflow (MAF) sensor. Without it, your car wouldn’t be able to adapt to changes in altitude because it is a component of the engine-management system.

What To Do When Check Engine Light Comes On

Rough idle, difficult starting, and an abrupt shift in the location of the accelerator pedal are all signs of MAF failure. Stalls and decreased gas mileage are other signs of a MAF issue. The normal cost of a MAF for a modern car is between $120 and $150.

What To Do When Check Engine Light Comes On, Causes #5: Vacuum Leak

There is a vacuum system in every car, and it serves several purposes. The vacuum system, which is used to activate the brake booster, also contributes to reduced emissions by directing exhaust fumes away from the engine. A vacuum leak may be to blame if the idle of your car surges or settles at an exceptionally high rpm. You can learn more in our guide on the P0113 Ford code.

As they get older, vacuum hoses can dry out and break, especially if they’re exposed to very hot or very cold temperatures. The most frequent reason for vacuum leakage is this. Other frequent problems include weak connections and broken fittings. Although vacuum lines are inexpensive, finding the leak’s source can be time-consuming and expensive if you hire someone to do it for you.

What To Do When Check Engine Light Comes On, Causes #6: EGR Valve Failure

The exhaust gas recirculation (EGR) system improves the efficiency of the car’s engine by reducing the amount of nitrogen oxide that is released. It facilitates fuel combustion by returning hot exhaust gases to the combustion chambers. It lessens emissions as well.

The EGR valve may clog up or stop working altogether (for more insight, check out our guide on what the EGR does in your car). The valve can be taken out, cleaned, and put back in relatively quickly if you have even a little mechanical aptitude. If the valve needs to be changed, budget at least $125 for a new, OEM-grade component.

What To Do When Check Engine Light Comes On, Causes #7: Dead Battery

The battery is both simple and crucial since, without it, your car won’t start. Batteries of today are maintenance-free and last a lot longer than they did in the past. Depending on the sort of vehicle you drive, the cost of a new one varies, but you should budget at least $100 for a good battery.

Dead Battery

Although changing or charging a battery on your own is a pretty simple process. Keep in mind that in some recent models of cars, the battery may be hidden beneath numerous plastic covers and may be a bit challenging to access.

Be aware that your stereo system will frequently be reset if you disconnect the battery. Before you unbolt the positive and negative terminals, ask your neighborhood dealer for the code if you don’t already have it. You’ll be driving silently if not.

Flashing Check Engine Light Then Stops

The most common cause of a flashing check engine light is cylinder misfiring. Misfiring should be looked at and fixed right away, which is why the light flashes rather than staying on. It can harm the catalytic converter and necessitate more expensive repairs. Misfiring can have many different reasons, some of which are commonplace like old, worn-out spark plugs.

If not, there can be a problem with your fuel supply system, ignition system, or another sensor. To be certain of the issue, you must have it diagnosed by a trained technician.

The service engine or check engine light on your dash light may flicker a few times before turning off. This is frequently a sign that a diagnostic trouble code (DTC), has been produced by the engine’s computer and saved in memory.

Check Engine Light Reset

By using an OBD2 scanner, you may reset the check engine light in the simplest manner possible. However, if one is not available, you can usually do without one. Here are some methods for turning off your check engine light.

1. Turning the Ignition On and Off

A simple trick to turn off the check engine light is to perform a hard reset. This can be done by turning the ignition on and off repeatedly. After inserting the keys, turn the ignition on and off one at a time, waiting a second between each.

Turning the Ignition On and Off

Once it is finished, check to see if the engine check light is still on. You are prepared to go if the check light is out. But if it is still coming on, you should be ready by scanning the codes.

2. Using An OBD2 Scanner

Your check engine light can be quickly reset if you have access to an OBD2 scanner. Connect the scanner to the OBD connector found beneath the steering column of the majority of cars. Next, turn the ignition on in your car. Press the “read” button on the scanner to go through all of the stored fault codes after the computer and car have connected.

After the scan is finished, write down all error codes that the scanner identified. Then utilize the user manual for that particular make and model to decipher those issues. The issue is identified after the code has been deciphered. The next step is to fix the issue. If the component needs to be replaced, do so; if it needs to be calibrated, perform the calibration.

Once finished, click the “Erase/Clear” button to remove the error from the scanner. After the issue has been resolved, it is advised to turn off the ignition, then turn it back on. Check to make sure the engine check light is not on again. Further, recheck using the scanner to see if the issue is still present or not.

3. Disconnecting The Battery

Without a scan tool, disconnecting the battery for 30 to 60 seconds is the most effective approach to turning off the check engine light. In many car models, this will reset the engine control unit.

Remove the negative terminal from the car’s battery first. Then, try to exhaust any remaining electricity in the capacitor of the car. This can be done by sounding the horn for 20 to 30 seconds or turning on the lights. After the electricity has been disconnected, leave your car for 10 to 15 minutes.

Once this little period has passed, reconnect the battery terminals. Check to make sure they are securely fastened to prevent any potential sparking, and then start your car.

After restarting, if your car still displays the check engine light, there may be a significant issue with it. Or the automobile may have stored the codes. Some car models won’t allow the codes to be reset by cutting the power in this situation. Hence, it is strongly advised to check the codes with a scanner instead.

4. Removing And Inserting The Fuse

The engine control unit’s fuse can be removed and then reinstalled as one method of turning off your check engine light. Although this won’t fix the issue in newer cars, it might in somewhat older cars, and it’s simple to test. For help locating the fuse for the engine control unit, consult your repair manual.

5. Check Engine Light But No Code

Your dashboard’s check engine light is a warning sign that something is wrong. In most situations, you would get out your car code scanner and determine the source of the problem. So what do you do if there are no diagnostic codes that indicate what the issue is?

There are reasons why the light may be on even when no codes are present, notwithstanding the rarity of the situation.

If you are unable to read any codes, your scanner is either the wrong one for your car or incompatible with it. The light turning on for no apparent reason could potentially be caused by an electrical short or blown fuse. Also, take into account the possibility that a contaminated port or user error is to blame.

6. Check Engine Light After Oil Change

The oil fill cap or dipstick is typically to blame when the check engine light illuminates following an oil change. If not, it can be because of low oil pressure, too much oil in the system, the use of the incorrect oil, or a sensor that wasn’t reset.


The check engine light gives a general sense of what’s wrong with a car. Sometimes in a precise or maybe in a hazy manner. It cannot, however, take the place of regular maintenance or a qualified mechanic. In conclusion, as soon as your car’s check engine light illuminates, you should have it inspected to prevent further, more expensive engine damage or a breakdown.

The fundamental requirements for your car, such as how frequently to change the coolant and oil as well as the brake pads, should also be known to you. Long-term time and financial savings can be achieved by doing a little research on your particular vehicle and its fundamental mechanics.

The upkeep of a car can be divided into two steps. Preventative maintenance is the first and most important. If you follow a regular maintenance schedule religiously, you might never even notice the tiny orange engine light turn on.

Frequently Asked Questions

Why Is My Check Engine Light On

The check engine light might illuminate for a variety of causes. For instance, a simple issue like a loose gas cap can cause a warning to appear. Additionally, serious issues like damaged internal engine components can turn on the light. It’s better to have a professional diagnose the problem with your car in order to truly understand what is wrong.

How To Reset Check Engine Light

Driving and time are the first and simplest ways to turn off the check engine light. The majority of onboard computers will check the issue that triggered the light several times. Just like you would usually, drive your car. After three days, if the light is still on, you could have to get the car further checked by a professional.

What Does Service Engine Soon Mean

The Service Engine Soon light indicates a system malfunction with the fuel, transmission, ignition, or emissions system. This might not be just a simple repair or maintenance issue. Ignoring these warning signs might result in major issues. A total breakdown, expensive repairs, and more including replacement of parts would be necessary.

Why Is My Check Engine Light Flashing

A considerably more serious problem is indicated by a flashing check engine light. Most frequently, it indicates a misfiring engine and unburned fuel entering the exhaust system. The catalytic converter’s temperature rises as a result, which may seriously harm it.

How To Reset Check Engine Light Without Scanner

Without a scanner, you could unplug the negative battery cable from the engine and wait a few seconds to reset the light. Your car’s diagnostic system will be reset as a result, and if the underlying problem has been fixed, the light should go off right away.

How Long Can You Drive With Check Engine Light On

Depending on the problem that caused the check engine light to come on, you could be able to keep driving for a very long time or only a few days. The engine computer has time to reset some sensors after traveling between 50 and 100 miles, which could resolve the issue.

What Is The Most Common Reason For Check Engine Light

Every time an oxygen sensor fails, a check engine light will come on. In fact, it’s among the most frequent causes of a check engine light appearing while you’re operating your car.

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