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5 Most Common Reasons for a Check Engine Light

- Last Edited: Aug 27, 2023
- Popularity: 67,720 Views


The Check Engine Light or Service Engine Soon Warning Light is one of the most frustrating and confusing warnings for vehicle owners.

A steady warning light means there is no immediate cause for alarm, but you should still get it checked out. A flashing warning light means that the problem is more serious, and you must check for codes.

1. Loose or faulty gas cap. This is the most common reason for a check engine light to come on. The gas cap helps to keep the fuel vapors from escaping the fuel tank, and if it's loose or faulty, it can cause the check engine light to turn on.

2. Oxygen sensor failure. Oxygen sensors measure the amount of oxygen in the exhaust gas, and they help the car's computer to adjust the air-fuel mixture. If an oxygen sensor fails, it can cause the check engine light to turn on.

3. Catalytic converter failure. The catalytic converter helps to reduce emissions from the car's exhaust, and if it fails, it can cause the check engine light to turn on.

4. Spark plug/ignition coil issues. Spark plugs and ignition coils help to ignite the fuel in the car's engine, and if they're not working properly, it can cause the check engine light to turn on.

5. Mass airflow sensor failure. The mass airflow sensor measures the amount of air entering the car's engine, and it helps the car's computer to adjust the air-fuel mixture. If the mass airflow sensor fails, it can cause the check engine light to turn on.

If your check engine light comes on, it's important to have it checked by a mechanic as soon as possible. The sooner the problem is fixed, the less likely it is to cause further damage to your car.

Here are some other possible reasons for a check engine light:

      • Engine misfires. This can be caused by a number of things, including bad spark plugs, ignition coils, or a dirty air filter.

      • Fuel system problems. This can include problems with the fuel pump, fuel injectors, or fuel filter.

      • Exhaust system problems. This can include problems with the catalytic converter, muffler, or exhaust manifold.

      • Vacuum leaks. A vacuum leak can cause the engine to run lean, which can trigger the check engine light.

      • Transmission problems. This can include problems with the transmission fluid, transmission sensors, or transmission solenoids.

If you're not sure what's causing your check engine light to come on, it's best to have it checked by a mechanic. They will be able to diagnose the problem and recommend the best course of action.