Motion & Emotion

Most Common Causes of a Check Engine Light


Is your check engine light on? It could activate for many reasons, some minor and some severe. Learn the common causes for a check engine light in our guide.

On your vehicle’s dashboard is a litany of lights that warn you if there are problems in the car. Perhaps the most crucial, though, is the check engine light. Learn more about the check engine light and its potential causes in our detailed explainer.

Flashing vs. Static Check Engine Light

First, before we get into the most common causes of a check engine light (CEL), you should know the difference between a flashing and a static CEL. A static CEL is much more common and means there’s a problem, but nothing too serious where you should immediately pull over and stop driving. Still, ignoring a CEL is one of the most common car maintenance mistakes drivers make.

If your CEL is flashing and is red or orange instead of yellow, your vehicle is experiencing a significant malfunction. A flashing CEL indicates that a massive engine failure is possible; you should pull over immediately and stop driving for your safety and everyone else on the road.

Common Causes of a Check Engine Light

A CEL activates when your vehicle senses something amiss in its system. The CEL, specifically, could be a response to a hundred different problems, but we’ve compiled a list of the most typical causes.

Faulty Spark Plugs

The spark plugs ignite fuel and air to create combustion and power the cylinders. After many years, though, the plugs can become worn down and faulty, leading to an engine misfire and overall poor performance in your engine.

If you notice your engine lagging and your CEL light is activated, the spark plugs could be the culprit.

Loose Gas Cap

Your vehicle’s gas cap isn’t just to keep a lid on your tank—it also keeps gasoline fumes from escaping and maintains the needed pressure in the fuel system. If your gas cap is leaking or loose, your car will activate the CEL as a warning.

Catalytic Converter Problems

The catalytic converter’s responsibility is to turn carbon monoxide into carbon dioxide, reducing the emissions output of your vehicle and improving its fuel economy. Various issues can cause problems with your catalytic converter, but your fuel economy and engine performance will suffer if it’s not functioning correctly.

Defective Mass Airflow Sensor

The Mass Airflow Sensor (MAS) measures the amount of air entering the engine to determine the correct amount of fuel the engine requires. The MAS is susceptible to dirt and grime buildup, so it could malfunction and activate the CEL if it needs to been cleaned.

Common symptoms of problems with your MAS include the engine idling roughly or reduced gas mileage in your vehicle.

Those are some of the most common causes of a check engine light, but there are many more—some minor and some more severe. Even if your vehicle seems to operate fine, a CEL activates for a reason, and you should get it checked by a professional as soon as you can.


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