If you’ve had this question, you’re not alone. It happens to the best of us. We’re driving along and minding our own business when our check engine light goes on. But did you know that there are a variety of reasons your check engine light can go off – from things as simple as a loose gas cap to issues more serious like a faulty alternator. If you’ve ever had this question, then keep reading as we cover some common reasons your check engine light turns on.

A Loose or Faulty Gas Cap

That’s right. Not tightening your gas cap can cause your check engine light to turn on. Your gas cap and the valves in your gas tank keep gas from escaping. If your gas cap is loose or faulty, it may cause you to lose gas due to evaporation, or cause your fuel to circulate improperly.

Check engine light & Faulty Alternator

If your alternator is faulty, you know it right away because you won’t be able to keep driving. Your alternator works with your battery to provide power to the car’s electrical system. When your alternator is faulty your car radio will turn off, your lights will dim, and you’ll lose the ability to drive (your power steering and brakes will go out). If your check engine light turns on for this reason, your next call will be for a tow.

Faulty Catalytic Converter

Your catalytic converter changes carbon monoxide to carbon dioxide which protects the environment. When there’s an issue with your catalytic converter, you’ll experience reduced fuel efficiency, and increased emissions. A faulty catalytic converter does not always need replacing – most often it’s caused by another issue like a blown head gasket which can force burnt coolant vapor into your exhaust.

Dirty MAS Airflow Sensor

Your MAS airflow sensor determines how much fuel is needed to run the engine, and measures the amount of air entering the engine. The airflow sensor can be susceptible to dirt and oil buildup, so it may just need a cleaning. A faulty MAS airflow sensor can cause your air to fuel ratio to be off which can cause failures in other areas of the engine.

Oxygen Sensor Failure and Why the Check Engine Light comes on

Your oxygen sensor measures the amount of unburnt oxygen in your car’s exhaust. The sensor sends data to your car’s computer which uses the information to regulate the mixture of air and fuel that enters your engine’s cylinders. If your oxygen sensor fails your car can keep running, but it will burn more fuel. If neglected over time, it can damage your spark plugs, and your catalytic converter.

Ignition Coils

Your ignition coils deliver an electrical pulse to each spark plug. When the engine’s computer sends a signal, the ignition coils release pent up energy to the spark plugs. Ignition coils are prone to failure after several years and cause your check engine light to turn on. Signs that your ignition coils need attention include poor fuel efficiency, and decreased engine power.

Fuel Injector Issues from the Check Engine Light

Each of your engine’s cylinders has a fuel injector, which is a small, electronically-activated valve that regulates how much fuel is sprayed into each engine cylinder during the intake cycle. Our fuel has impurities and when combined with carbon produced by the combustion process, it can cause the fuel injector to clog or plug. When fully clogged, the fuel injector can get stuck in the open position – causing it to continuously leak fuel into the cylinder, and making the engine run more roughly.

While there are a variety of reasons your check engine light turns on, these are a few of the most common causes. If your check engine light comes on, we recommend making an appointment so one of our mechanics can take a look, diagnose your problem, and get you back to enjoying your drive no matter where the road takes you.