The Check Engine Light: Common Causes and How To Fix It (2024)

When a yellow check engine light illuminates on a vehicle's dashboard, that means something may need immediate attention , but the question is: What?

This ominous light can signal something as simple as a faulty gas cap, or something more extreme like engine or exhaust malfunctions. Whatever the problem may be, pay attention to the check engine light, and service your vehicle as soon as possible when it comes on.

In this article, we will detail a few different reasons that a check engine light may turn on, and what you should do to get back on the road safely.

What Does A Check Engine Light Mean?

Unlike a general maintenance reminder, a check engine light is a warning indicator on the vehicle's dashboard that alerts the driver to a potential problem within the engine or the emission system.

There are varying degrees of severity as to what the issue could be , it may be something as simple as tightening the gas cap or something problematic with the engine. Whether you inspect the problem yourself or take the vehicle to a mechanic, it's important to resolve a check engine light promptly to maintain safety on the road.

Solid vs. Flashing Check Engine Light

The difference between a solid and flashing check engine light lies in the severity of the problem.

A solid check engine light is what most people encounter and may signal a minor or more complex repair. You should address this warning as soon as possible , however, it doesn't pose an immediate threat to your vehicle unless something is noticeably wrong. This indicator means that there is a problem with one of the engine systems, and it would be wise to schedule an appointment with a mechanic in the near future.

A flashing check engine light, however, may indicate a more serious problem than a solid check engine light. If this indicator is flashing, that means there is an ignition malfunction, with the most likely culprit being an engine misfire. Left untreated, this could potentially develop into a catastrophic problem for your vehicle.

If you are driving and a flashing check engine light turns on, it's important to be cautious and pay special attention to your vehicle's performance. If the vehicle is losing power, shaking, emitting a strange odor, or acting in an otherwise abnormal way, pull over as soon as it's safe to do so and inspect the problem yourself, or contact roadside assistance.

6 Possible Reasons Your Check Engine Light Is On

A check engine light is a common occurrence for drivers. While this indicator may or may not signal a significant problem, it's important to resolve the issue quickly.

Going to a repair shop can diagnose, give an estimate and solve the issue in-house. However, if you would like to get a better understanding of what may be wrong with your vehicle , or if you would like to fix it yourself , here are six common reasons the check engine light may come on.

1. Fuel Cap

The fuel cap, along with a series of lines inside of the gas tank, makes up a system that recirculates gasoline vapors and keeps them from escaping into the surrounding area. A loose or faulty fuel cap can result in unintended emissions, leading to the check engine light turning on.

Additionally, loose fuel caps can mean the gas in your tank is evaporating before it can be used. Therefore, it's important to address this issue to not only to resolve your check engine light, but to also save money on wasted gas.

2. Oxygen Sensor

An oxygen sensor is part of a vehicle's emission control system that helps to regulate the air to fuel ratio in the engine and reduce harmful emissions. This part is typically located in the exhaust pipe, and sends a signal to the engine control module if the air-fuel ratio needs to be adjusted.

If this part malfunctions, it will set off the check engine light. It's important to get this issue resolved quickly, because if this problem is left untreated, it can cause your vehicle to burn more gasoline than is needed, resulting in a steep drop in efficiency and miles per gallon.

3. Catalytic Converter

A catalytic converter is an important component of a vehicle's emissions system, which converts harmful pollutants into less harmful substances, such as turning carbon monoxide into carbon dioxide.

A problem with the catalytic converter will set off a vehicle's check engine light, and if the issue goes unresolved, this can result in reduced vehicle performance and fuel efficiency.

However, it's important to note that if there's a problem with the catalytic converter, there is typically a problem elsewhere in the vehicle. In this case, replacing only the converter would likely not solve the issue.

4. Mass Airflow Sensor

The mass airflow sensor is a part that measures the amount of air flowing into the engine. This is an important component of a vehicle's emission control system and contributes to how much fuel gets injected into the engine based on the amount of air flowing in.

A problematic mass airflow sensor will not only set off the check engine light, but it will also contribute to reduced engine performance, reduced fuel efficiency, and may result in a rough vehicle idle or problems with acceleration. You will need to replace damaged sensors, but it may be as easy as cleaning the part to fix the problem.

5. Spark Plugs/Wires and Ignition Coils

Spark plugs are a component of a vehicle that produces the spark which ignites the fuel, thereby powering the engine's cylinders.

A faulty spark plug will cause the check engine light to turn on, and can also result in some easily diagnosable symptoms such as misfiring and other emissions issues. Spark plugs , as well as spark plug wires in older vehicle models, or ignition coils in newer vehicles , are prone to degenerate through normal wear and tear. If this is the cause of the check engine light, fixing this issue will not only resolve the warning, but also improve vehicle performance.

6. Battery

As many know, the battery in a car provides electrical support to the vehicle. While today's car batteries last longer than ever, there can still be problems from time to time, resulting in the check engine light turning on.

If a car battery is not providing enough energy to a vehicle's electrical system, it can trigger electrical malfunctions , not to mention, the vehicle can have difficulties starting or maintaining performance.

What to Do When Your Check Engine Light Comes On

When your check engine light comes on, it's important to resolve the problem promptly. After all, it may be a quick fix, or it could be an issue that needs attention as soon as possible.

Here are three things you can try to safely remove the warning indicator and get your vehicle back on the road.

Check For Any Easy Fixes

A check engine light can come on for a number of reasons, with some of them being very minor fixes. A few easy self-diagnosis methods include:

• Check the gas cap: A loose gas cap can affect a vehicle's emission control systems, potentially causing a check engine light to turn on. Make sure your gas cap is screwed on tightly.
• Review maintenance records: Has your vehicle recently returned from a body shop or mechanic? Contact the business to potentially determine the source of the check engine light , it may be as simple as manually resetting your vehicle's system.
• Investigate for anything abnormal: While not an easy fix, checking for any abnormal issues can shed light on if the check engine light is a serious problem. Look for things such as unpleasant odors around the vehicle, or take note if the vehicle is not running smoothly.

Visit A Repair Shop

If you cannot easily fix the issue that illuminates your check engine light, or if you are unsure of the issue, the best course of action is to talk with a repair shop.

Whether there is an issue with your vehicle's emission system, or something more serious such as engine problems , these professionals have the tools to easily diagnose what is wrong with your vehicle.

Use our AAA-approved facility locator to find a nearby mechanic that can get you back on the road.

Use an OBD2 Scanner

Another way to diagnose a check engine light is by using an OBD2 scanner.

An onboard diagnostics scanner (OBD2) troubleshoots problems within a vehicle, and can alert mechanics and at-home users to issues with the engine, exhaust system and a variety of other problems. These tools work by plugging into an electrical port underneath the dash on the driver's side, and works on most vehicles made after 1996.

You can find this helpful tool at auto parts stores, and it can help to identify the cause of a check engine light.

Check Engine Light FAQs

Finally, here are a few other frequently asked questions regarding check engine lights.

Is a Check Engine Light Serious?

A check engine light may be serious, so it's important to inspect your vehicle as soon as possible. While this warning indicator can arise from simple fixes like inflating the tires or tightening the gas cap, it is best to err on the side of caution and promptly find the cause of the problem.

Is It OK To Drive With a Check Engine Light?

While you should resolve the issues for your check engine lights quickly, it is OK to drive short distances with the warning indicator, as long as nothing is noticeably wrong with the vehicle.

However, if your check engine light is flashing, the car is driving abnormally or if there is smoke or strange odors, you should pull over immediately and shut off the engine.

What if the Check Engine Light Is on, but the Car Runs Fine?

Check engine lights can turn on for a number of reasons. Some can be minor problems such as tightening the gas cap, and others can be serious problems like engine issues. If your vehicle is running fine, the check engine light may signal a minor issue, but it is best to visit a mechanic to make sure.

You should not overlook a check engine light. While it may be signaling a minor issue, it's important for the safety of your vehicle and your passengers to find the problem as soon as you can. If your vehicle is in need of repair, find an AAA-authorized technician in your area to get you safely back on the road.