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What Causes the Check Engine Light to Come On?

The yellow outlined symbol of an engine is most drivers' biggest nightmare. It means that your car is in trouble, and it usually requires you to take your vehicle to the repair shop. Let's take a look at the top 5 common causes that will trigger your check engine light:

Catalytic Converter

Out of the five problems we are going to talk about, this one is the most dreaded. The reason for that is because it can be costly to replace the catalytic converter, and your vehicle needs it. The catalytic converter is a portion of your car's exhaust system known for its chemical converting capabilities. If you notice a rotten egg odor along with the check engine light, the cat is probably the problem.

Loose Gas Cap

If you happened to forget to screw on your gas cap last time you filled up your car, SUV, or truck, then it will cause your check engine light to come on. If there's a gap for any other reason, such as a damaged cap, please have it replaced as soon as possible.

Mass Airflow Sensor

The MAF sensor in your engine is the piece that measures the air coming into the motor and proportionally allocates it according to the amount of fuel. If you aren't getting the precise air/fuel mixture, your engine might malfunction. When the mass airflow sensor fails, the check engine light will come on when the onboard computer learns that the air/fuel mixture is corrupted.

Oxygen Sensor

Similar to the MAF sensor, the oxygen sensor experiences the same thing. The O2 sensor measures how much unburned oxygen is present in your exhaust. If there's too little or too much o2, it could damage your engine parts. A damaged oxygen sensor will result in a check engine warning light every time. This is one of the most common reasons why a check engine light may come on.

Spark Plugs

Lastly, old or ineffective spark plugs will cause your check engine light to come on. If you haven't had your plugs swapped out in a while and your vehicle has more than 100,000 miles on it, it's time for new plugs! Another sign of aging spark plugs is engine stalling.


If you need check engine light repair, please do not hesitate to bring it to our expert team at Folsom Automotive Service.