The 7 Most Common Reasons Your Check Engine Light Turns On

Any time a warning light in your dashboard lights up, it grabs your immediate attention. While warning lights have been around for years, today they have become more sophisticated and there are more of them on your dashboard than ever before.

That’s good news for drivers, because it means you are less likely to let your car run low on oil or let the air pressure in your tires dip below recommended levels. It lets you know when there’s a problem with the battery, the engine coolant or even if there’s a door that’s not securely latched.

However, when the check engine light comes on, it can mean several different things, and it sometimes causes a bit of a panic for drivers. But if you understand what it means, it might give you a bit more reassurance — as well as the knowledge of what to do when it happens.

Let’s look at the seven most common reasons your check engine light turns on.

No. 1: Gas Cap

A loose, missing or damaged gas cap can cause the light to turn on because the vehicle’s onboard computer recognizes that it is losing pressure in the gas tank. A gas cap helps maintain proper pressure in the tank and also keeps the gas from evaporating, as well as preventing fumes from being released into the air. If your check engine light goes on shortly after you’ve filled up at a gas station, check to make sure the gas cap is on tightly (or that you remembered to put it back on!) and that may resolve the problem. If not, it could be one of the other following problems.


No. 2: Spark Plugs or Plug Wires

Your car depends upon spark plugs to fire up the engine, and the spark plug wires are the delivery system that makes it happen. When either of these are compromised, your engine can’t perform as well; you may have less power and lower fuel economy and your engine may misfire, among other problems.


No. 3: Catalytic Converter

Emissions are a great cause of concern in today’s world, and that’s one reason the catalytic converter is so important. It converts dangerous carbon monoxide into carbon dioxide and, without this important function, your car will not pass the vehicle emissions test required for registering with your state department of transportation. A damaged catalytic converter or a clogged catalytic converter can also lower your fuel economy and cause your car to run at a hotter temperature.


No. 4: Oxygen Sensor

The oxygen sensor plays an important role in your vehicle’s operation because it monitors the unburned oxygen that comes out of your exhaust. That allows it to help your car accurately monitor fuel consumption. A faulty sensor can greatly reduce your fuel efficiency and can even cause damage to your spark plugs and catalytic converter.


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No. 5: Mass Airflow Sensor

The amount of air entering your car’s engine will determine how much fuel is required to run efficiently. It’s the job of the mass airflow sensor to measure the air and instruct your car’s computer on how much fuel it needs. When a mass airflow sensor isn’t functioning properly, some of the results will be diminished engine performance and lowered fuel economy. But if not taken care of, this can also damage spark plugs, your oxygen sensor and your catalytic converter.


No. 6: Overheating

Chances are, if your check engine light comes on because of overheating, you’ll notice some other signs as well — such as the temperature gauge running high or even smoke coming out from under your hood. Since this could be a severe problem, it should be addressed immediately. Slow down and you may want to turn on the heater as a way to release some of the heat from the engine. If this doesn’t help, you may need to pull over and call for roadside assistance.


No. 7: Diagnostics Malfunction

Sometimes, the check engine light comes on to let you know that there’s a problem with the car’s internal diagnostic mechanism. That means the system could be “finding” a problem that doesn’t exist, or it could be that loose wire systems are creating a false positive in the system. If that’s the case, it’s important to get it fixed because you want to know that your car’s operations are being consistently monitored by the onboard computer — and that it will accurately alert you to any malfunctions that are occurring.


Never Ignore Your ‘Check Engine’ Light

While there are a variety of reasons that your check engine light might come on, it’s important to note that if the light is flashing, it indicates that your engine has a major issue that must be addressed immediately. If the light is a steady glow, that indicates a less urgent problem, but it still should be taken in for diagnostics and service.

Either way, attending to the warning light in a timely manner will prevent any additional damage from occurring to your car. Even if it seems that the car is running “just fine,” you want to have it checked out professionally to rule out any underlying problems that could lead to costly repairs down the road if not taken care of promptly. Sometimes, it’s easy to get a false sense of security when the light comes on and you don’t notice any changes in the car’s performance, but this is a dangerous gamble for any driver to take.

The specific reason your check engine light has come on can only be discovered through the use of special car diagnostic equipment. Be sure to visit your local Cleveland-area auto repair shop for an inspection to see what's going on with your vehicle.

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