The Top Reasons Your Car's 'Check Engine' Warning Goes On

Find out what that light on the dash probably means -- and what it could cost you.

Car dashboard warning lights symbols amstockphoto / Shutterstock

You're on the road, and suddenly -- Oh no! Your car's "check engine" light just came on, warning that something's wrong.

But what exactly does it mean? And will fixing the problem be so expensive that you'll need to dip into your emergency savings? (Let's hope you remembered to set up your emergency fund.)

Check-engine repairs aren't cheap, costing an average of $381, according to the 2019 Vehicle Health Index from CarMD. That price tag has gone up about 7% in a year.

Here's the latest ranking of the most common reasons for that dreaded dashboard warning indicator, counting down to the most frequent problem. The average repair bills include parts and labor.

10. Replace your thermostat

Hand a man put car thermostat for service
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Thermostats can fail due to rust or other issues.

Average repair cost: $245

The thermostat helps regulate the temperature of the engine so it doesn't overheat. The device needs to open and close to operate properly, but sometimes the thermostat gets stuck in the open position.

When this happens, the car's computer can't tell if the engine coolant is reaching the proper operating temperature, and that triggers the check-engine light. Rust, a failure to change the coolant, and extreme temperatures are common causes of thermostat failure.

This problem accounts for 2.4% of all check-engine repairs, and the cost has gone up 8.9% since CarMD's 2018 report.

8. (tie) Replace your fuel injectors

Car mechanic fixing fuel injector at  two camshaft gasoline engine
sima / Shutterstock
Faulty fuel injectors can lead to all sorts of problems.

Average repair cost: $450

Like the name implies, fuel injectors inject fuel into the engine. They have become incredibly refined and precise, and when a fuel injector fails it can result in reduced fuel efficiency, engine misfires and performance issues.

Many vehicle manufacturers have recently changed over to direct injection (DI) fuel systems, which use high-pressure injectors. These are generally better for fuel economy but are more prone to failure.

Injector failure is responsible for 2.78% of check-engine repairs; the cost has inched up 0.7% since the last survey.