What to Do if the Check Engine Light Is On?

Usually, the Check Engine light isn't a "Stop right now or you'll damage the car!" situation unless it's flashing. If the light is flashing, it means there's a more serious problem.

This little light on your dashboard can mean different things based on whether it is blinking or steady. Let's see what these signs could mean and what to do about them.

Here are some of the possible reasons why the check engine light might be on:

1. Faulty or loose gas cap

If the gas cap is loose, it can trigger the "check engine" light. This is one of the simpler issues to fix. A loose or missing gas cap can lead to fuel loss through evaporation or cause the fuel system to not work correctly.

2. Worn spark plugs

Spark plugs ignite the fuel and air mix to power your engine's cylinders. If they're not working properly, it can cause engine misfires, which increase emissions and reduce engine performance.

3. Dirty or faulty mass airflow sensor

The mass airflow sensor (MAS) measures how much air is entering the engine to determine the necessary fuel amount. It can get dirty or oily, so cleaning it might solve the problem. If not, it might need to be replaced. When the air-to-fuel ratio is incorrect, it can cause engine problems, reduce performance, and lower fuel efficiency.

4. Faulty catalytic converter

The catalytic converter transforms carbon monoxide into carbon dioxide to reduce harmful emissions. If it’s not working properly, your fuel economy and engine performance will suffer, and your emissions will increase, which might cause you to fail emissions tests. 

Replacing the catalytic converter alone usually isn’t enough because its failure is often due to another problem, like a blown head gasket, which can send burnt coolant vapor into the exhaust system.

5. Oxygen sensor

The oxygen sensor checks and measures how much fuel the car burns. Most cars have two to four oxygen sensors, and if any of them are faulty, the engine light could come on. A bad sensor will lower gas mileage and increase emissions, and if not fixed, it can damage the catalytic converter, leading to costly repairs.

6. Dirty thermostat

The thermostat in your car controls the flow of coolant to the engine. If the coolant gets dirty or contaminated, it can become corrosive and cause the engine to overheat.

A coolant leak can also cause the engine to overheat and trigger the warning light. Leaks are easier to spot because you'll see greenish drops or puddles under your car after it's been parked for a while.

The cost to fix a check engine light can vary widely, from very little to thousands of dollars. The sooner you get your vehicle checked, the less chance there is of more damage happening.