You’re driving along, music blasting, windows down, not a care in the world. Then—bam!—that dreaded yellow Check Engine Light pops up on your dash (pictured above). Your heart sinks. Is your car about to self-destruct? Will you be stranded on the side of the road? The good news? It’s probably something minor. The bad news? It could be serious. Here’s what that little glowing nightmare actually means—and what you should do about it.

What does your car’s “Check Engine” light really mean?

Your Check Engine Light is a legally-required emissions warning. Something is polluting—maybe a loose gas cap, maybe a failing engine. Either way, it’s serious. Ignoring it could mean poor fuel economy, costly repairs, or even a breakdown. Get it checked ASAP.

Your car’s onboard computer is always monitoring emissions. If something throws off the system—bad fuel, a misfire, or even a failing sensor—it flips the light on. Because emissions laws are strict, even minor issues will trigger it. That means anything from a clogged air filter to a busted catalytic converter could be the culprit.

Luckily, getting answers is easy. Most auto parts stores will read your car’s trouble code for free. Instead of stressing or paying a mechanic just to check it, swing by your nearest parts store and find out what’s really going on. You’ll have answers in five minutes.

What is the most common cause of a Check Engine light?

A loose gas cap. No, really. The system that keeps fuel vapors from escaping is part of your emissions setup. If the gas cap isn’t sealing properly, your car thinks it’s polluting and flips the light on.

Before you panic, tighten the cap and drive a few miles. If the light turns off, problem solved. If not, it could be something bigger—like bad spark plugs, a faulty oxygen sensor, or a clogged catalytic converter.

Even though a loose gas cap is the most common cause, don’t assume a Check Engine light is always minor. Some serious problems—like an engine misfire—can also trigger the light. That’s why it’s always worth checking out sooner rather than later.

Is it OK to drive with the Check Engine light on?

If the light is steady, you can keep driving—just don’t wait too long to check it out. If it’s flashing, pull over immediately. Shut your car off. And call for help.

A solid light usually means a minor issue, but it can still affect performance and fuel economy. Get it scanned at your earliest convenience.

A flashing light? That’s a red alert. For example, it could mean a major misfire is dumping unburned fuel into the exhaust. This is a major safety problem Left unchecked, this can overheat and destroy your catalytic converter—a repair that can cost more than $1,000. It could also mean a major internal issue is on the verge of damaging your engine irreparably. If the light is flashing, don’t risk it—stop driving and call for help.

Bottom line: The Check Engine Light isn’t always a disaster, but it’s never something to ignore. Whether it’s a simple fix or a major repair, catching it early can save you money and keep you on the road.