What a check engine light means & how to fix it

By Allstate

Last updated: October 2022

So, you're driving along and suddenly, the check engine light comes on. This can bring several questions to mind. Should you stop driving immediately? What's wrong? Is it serious? Do you need to call a tow truck? How much will this cost?

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What the check engine light means

A vehicle's check engine light can turn on for many reasons, ranging from a minor issue to a serious problem. Before trying to troubleshoot the problem, keep in mind what the check engine list signifies. As Consumer Reports points out, the check engine light means that the vehicle's electronic control system has identified a problem that it can't correct automatically.

After the light is triggered, a trouble code is stored in the car’s computer memory to properly identify the issue. This code can be read by a diagnostic tool carried by most auto repair shops. A qualified mechanic can read the code, diagnose the problem and in most cases repair your vehicle.

According to motorist.org, some manufacturers and vehicle models have different warning lights to indicate the severity of the problem. The check engine light may either blink or remain constant.

Flashing check engine light vs. static

If the light is steady, it may not be an emergency, but you should get the problem checked out by a mechanic as soon as possible. However, a blinking light usually indicates a severe engine misfire, which allows unburned fuel to be dumped into the exhaust system. This can cause extensive damage and result in costly repair bills.

Can I check my own check engine light?

You could check your own engine light with an onboard diagnostics (OBD) scanner. An OBD-II is the most up-to-date version of the technology – and it pulls codes from your vehicle's computers to see what might be wrong in one of its components, says Forbes.

Common causes

The Family Handyman has compiled a list of common causes of a check engine light. These include:

  • Loose, damaged or missing gas cap.
  • Failed or failing O2 sensors.
  • Spark plug, wiring or ignition issues.
  • Catalytic converter failure.

What to do if you're driving

Once your check engine light goes on, Consumer Reports identifies a few things you can do if you're driving when the light appears. First, you can check your dashboard gauges and lights to see if there's a low oil pressure warning or if your engine is overheating. If you find any of these problems, it's best to pull over as soon as it's safe to do so. These problems can be serious and create a dangerous situation for you and your vehicle.

Also, if you notice performance issues with your vehicle, it's a good idea to reduce your speed and the demands on your engine.

Since the check engine light can point to any number of issues, it's a good idea to have a qualified mechanic diagnose the issue as quickly as possible. That way they can fix the problem and get you safely back on the road.

Why you shouldn’t ignore a check engine light

Ignoring a check engine light could cause vehicle components to deteriorate and lead to costly – and dangerous – issues, down the road, says Reader's Digest. And once one system begins to fail, others may begin failing as well. That’s why it's recommended to bring your vehicle in as soon as the check engine light comes on.

How to fix check engine light

An OBD-II scanner can clue you in on what's going on with your vehicle. Some repairs may be simple – for instance, replacing a gas cap. But other engine problems may need to be addressed by an experienced mechanic. Once those problems are addressed, the light should turn off.

How to reset the check engine light

Depending on the OBD-II scanner, you may be able to reset the code, which could turn off the light, according to Forbes. But if the problem isn't addressed, the light will likely come back on again.

Check engine light FAQs