What Causes the Check Engine Light to Come On?

There are hundreds of possible trouble codes that can trigger the check engine light, but some are more common than others.

The check engine light is one of the most common and frustrating indicators on your car's dashboard. It can mean anything from a minor issue to a serious problem that requires immediate attention. But what exactly causes the check engine light to come on, and how can you fix it?

The check engine light, also known as the malfunction indicator lamp (MIL), is part of your car's onboard diagnostic system (OBD). The OBD monitors various components and systems in your car, such as the engine, transmission, emissions, fuel injection, and ignition. When the OBD detects a fault or a deviation from the normal operation, it stores a trouble code in its memory and turns on the check engine light to alert you.

Here are some of the top causes of a check engine light, according to Word Stream:

• Loose or leaking gas cap: This may seem like a trivial issue, but a gas cap that is not properly sealed can cause a leak in the fuel system, which affects the pressure and the emissions. This can also reduce your gas mileage and increase your emissions. To fix this problem, simply tighten or replace the gas cap and clear the code.

• Oxygen sensor failure: The oxygen sensor measures the amount of oxygen in the exhaust and sends this information to the car's computer, which adjusts the air-fuel mixture accordingly. A faulty oxygen sensor can cause your car to run rich (too much fuel) or lean (too little fuel), which can damage your catalytic converter, spark plugs, and other components. It can also reduce your fuel efficiency and increase your emissions. To fix this problem, you need to replace the oxygen sensor and clear the code. 

• Catalytic converter failure: The catalytic converter is a device that converts harmful gases in the exhaust into harmless ones. It is essential for reducing your car's emissions and meeting environmental standards. A failing catalytic converter can cause your car to run poorly, lose power, have poor acceleration, and emit a rotten egg smell. It can also cause your car to fail an emissions test. To fix this problem, you need to replace the catalytic converter and clear the code.
• Spark plug/ignition coil issues: The spark plugs and ignition coils are responsible for creating and delivering the spark that ignites the air-fuel mixture in the cylinders. When they are worn out or damaged, they can cause misfires, rough idling, poor performance, reduced fuel economy, and increased emissions. To fix this problem, you need to replace the spark plugs and/or ignition coils and clear the code.

• Mass airflow sensor (MAF) failure: The mass airflow sensor measures the amount of air entering the engine and sends this information to the car's computer, which adjusts the fuel injection accordingly. A dirty or faulty MAF sensor can cause your car to run rich or lean, which can affect your performance, fuel economy, and emissions. To fix this problem, you need to clean or replace the MAF sensor and clear the code.

These are just some of the possible causes of a check engine light. There are many other factors that can affect your car's performance and emissions, such as vacuum leaks, exhaust leaks, fuel injector problems, thermostat issues, etc. The best way to diagnose and fix a check engine light is to use an OBD scanner tool that can read and clear trouble codes. You can buy one online or at an auto parts store, or you can visit an auto repair shop near you that has one.

If you ignore or delay fixing a check engine light, you may end up causing more damage to your car and spending more money on repairs in the long run. You may also risk failing an emissions test or getting a ticket if you live in a state that requires periodic inspections. Therefore, it is important to take action as soon as possible when you see the check engine light on.

Remember that not all check engine lights are equally serious. Some may indicate minor issues that can be easily resolved by yourself or by a reliable auto repair shop, while others may indicate major problems that require urgent attention. If your check engine light is solid (not blinking), you can usually continue driving until you find a convenient time and place to get it checked out. However, if your check engine light is flashing, it means there is a severe issue that may damage your engine or catalytic converter. In this case, you should pull over safely and call for roadside assistance or tow your car to a nearby mechanic.

The check engine light is not something to be afraid of or ignore. It is a helpful warning system that tells you when something is wrong with your car and needs attention. By understanding what causes it and how to fix it, you can keep your car running smoothly and safely for years to come.

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