What Does Your Check Engine Warning Light Mean?

A check engine warning light can indicate a variety of issues, some easier to fix than others. Review this brief guide to understand this warning.
Written by Rachel Rigolino
Reviewed by Melanie Reiff
A check engine light—also called an engine warning light—can indicate a number of issues, from a loose gas cap or dirty spark plugs to a bad catalytic converter. 
A check engine light comes on because a sensor has indicated a problem with your vehicle’s engine or exhaust system. If the light is flashing, treat the situation as urgent and in need of immediate attention.
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What does the engine warning light look like? 

An engine warning light is an icon that looks like the outline of a small engine and it’s typically yellow, amber, or orange. In some vehicles, you may also see a message that reads: CHECK ENGINE.

What does the engine warning light mean?

There are many reasons that your check engine warning light may come on. What follows are some of the most common: 
  • Loose gas cap. Always begin here. Your gas cap not only keeps gas in your tank but also helps to ensure there’s enough pressure in your gas tank. If there's not enough pressure, a sensor will send an error message to your car’s central computer. Tightening the cap just might solve the problem.
  • Problems with one or more sensors. Often a failing sensor can cause the engine warning light to come on. A bad oxygen sensor is often the culprit, triggering the engine warning light when there is too much or too little oxygen in your exhaust system. However, other sensors go bad as well. You’ll need to connect your vehicle to an
    OBD II code reader
    to help determine which sensor is failing. 
  • Bad spark plugs and/or wires. Worn plugs and/or spark plug wires can cause your engine to misfire, which will then send a signal to your vehicle’s computer that something is wrong with the way the engine is running. Examine your spark plugs to see if they’re corroded or dirty. 
  • Bad Catalytic Converter. Your catalytic converter is part of your exhaust system and helps with reducing the air pollution created by combustible engines. In other words, it cleans up your car’s engine exhaust. If you don’t fix or replace a bad catalytic converter, you won’t be able to pass an emissions test—even if you don’t outright notice problems with your vehicle. 

How to turn off your engine warning light

Before taking your vehicle to a mechanic and possibly spending too much money on
car repairs
, try tightening your gas cap
If your light is still on, take your car to a mechanic or use an OBD II reader to help diagnose the issue that’s causing the check engine light to come on. Follow these steps:
  • Conduct a scan with your OBD II reader to find the code associated with the engine warning light.
  • Write down the code(s) given to you by the reader.
  • Fix the issue yourself and/or report what you have found to your mechanic.
Some car owners are comfortable with replacing sensors, for example, especially if they are located in easy-to-access sections of a vehicle.

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A check engine warning light can indicate a variety of issues. While some of these problems are easy to address, others are more complicated.
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