My Check Engine Light Is On — What Does It Mean?

What does the check engine light mean? It can illuminate due to anything from a loose gas cap to something more hazardous, like a misfiring engine.
Written by Brenna Swanston
Reviewed by Kathleen Flear
The check engine light alerts you when there is something wrong with your engine. It could be anything from a loose gas cap to something more hazardous, like a misfiring engine.
Since your
car insurance
typically won’t cover regular maintenance on your vehicle, you’ll want to figure out what’s going on right away to avoid costly damage.
Not sure how to decipher that mysterious little dash light? That’s why
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What does the check engine light mean?

The check engine light is an indication that your car's emissions, ignition, fuel, or exhaust systems are experiencing an issue.
Cars are run by an engine computer unit (ECU) that controls the car's auxiliary systems and drive train. The ECU receives input from the car's sensors. If the ECU detects an issue it can't self-correct, it illuminates the check engine light.
Depending on the make and model of your car, your check engine might be in the shape of an engine or just read "check engine." It’s normally yellow, orange, or amber.

What does it mean when the check engine light flashes?

Pay attention to whether your check engine light is solid or flashing.
  • A solid light usually means that you should get your car checked by a mechanic as soon as possible—but it's likely not an emergency that requires immediate attention.
  • A flashing light generally means that your car needs immediate attention.
In some car models, the check engine light may turn red to indicate a serious problem. In this scenario, you should consider pulling over and
having your car towed
to a local mechanic—especially if you notice a decrease in your car’s performance.
Key Takeaway The check engine light lets you know when something is wrong with your car’s emissions, ignition, fuel, or exhaust systems.

Why is my check engine light illuminated?

There are a number of reasons that your check engine light could be illuminated, ranging from something harmless to something serious.
On rare occasions, your check engine light may come on and there is nothing wrong. This is caused by humidity changes and the light will turn off by itself (lucky day!).
But if that isn’t the case, here are some possible reasons why your check engine light is on.

Loose gas cap

When the gas cap is loose or damaged, it sends a message to your car's computer that there's a leak in the vapor recovery system. A loose or
damaged gas cap
will trigger a check engine light because its normal vacuum seal is broken.

Catalytic converter going out

The catalytic converter is a part of the exhaust system. It converts carbon monoxide to carbon dioxide to lower your emissions and protect the environment. Your car can't operate if it malfunctions.

Worn spark plugs or plug wires

spark plugs
and plug wires are attached to your car's ignition system. An issue with your spark plugs and/or wires means you probably need to replace one or both. If your car stalls, it can also be an indication that there's something wrong with the spark plugs.

Failing oxygen sensors

The oxygen sensors measure unburned oxygen in the exhaust system. You can still drive if the oxygen sensors fail, but you should get them replaced as soon as possible.

Engine misfire

An engine misfire is a serious (and potentially hazardous) issue that can cause your engine to smoke. If this happens, pull over immediately.
Key Takeaway Your check engine light could illuminate due to something as simple as a loose gas cap—but it could also indicate something far more serious.
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What to do about the check engine light

If your check engine light comes on, don’t panic. Here are a few things you can try:
Reduce your speed and pull over. This is especially important if you're driving and your light begins to flash.
Tighten (or check) your gas cap. After tightening the cap, drive as normal. If the problem was a loose gas cap, the light will turn off on its own in a day or so, after a few engine restarts.
Check for overheating or another serious issue. Are there any other warning lights going off? If so, pull over, shut off the engine, then try to restart your car. If that doesn't work, call
roadside assistance
or a tow truck.
Ignoring the check engine light could lead to big repair costs down the road (literally). Address the issue promptly and save yourself time, money, and a headache.
Key Takeaway Whatever you do, don't ignore the check engine light.

Does your insurance cover you for mechanical issues?

If you have
mechanical breakdown insurance (MBI)
, you might be covered for issues indicated by your check engine light if they aren't a result of normal wear and tear.
Not all insurance companies offer MBI, so check with yours to see if it’s an option. If you’re eligible, the insurance would cover your car’s major systems and could save you big money on repairs.
If your check engine light comes on as a result of a fender bender, you might be able to file a claim under your
collision coverage
. Depending on your policy, it could cover all or most of the costs.
Key Takeaway Mechanical breakdown insurance or collision insurance might cover the cost of mechanical repairs, but it depends on the root cause.

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Is it safe to drive your car with the check engine light on?

It depends on your car's performance. If you notice any performance issues and your light is on, consider pulling over and towing your vehicle to a local mechanic.

Can low oil cause the check engine light to come on?

No. If your car is low on oil it will trigger the low oil light, not the check engine light.

Can I ignore the check engine light?

You should never ignore the check engine light when it comes on. This light means that there is something wrong with a vital function in your car, and ignoring it could be costly in the long run.
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