Top 10 Check-Engine Light Repairs

CARS.COM — When the light goes on, something’s wrong. The vehicle diagnostics analysts at CarMD released their 2017 report on the most common car repairs resulting from that dreaded check engine light illumination, with faulty oxygen sensors again topping the list of culprits.

Related: Should I Worry About How Hot My Engine Is Running?

CarMD’s 2017 Vehicle Health Index is based on repair data from more than 5.3 million cars, covering 2016. The study found that the average repair resulting from a check engine alert cost $398 in 2016, up 2.7 percent from the year before and ranging in cost from $17 to nearly $1,200. Among the four designated regions, only the West experienced a price dip, of 1.1 percent, while the Northeast paid the highest repair bills at an average of $401 and the Midwest the lowest at $385.

Here are the top 10 most common repairs resulting from a check engine light plus the average cost for parts and labor:

10. Replace Evaporative Emissions Purge Solenoid

What is it? It helps control how much fuel vapor escapes into the atmosphere.

What’s the damage? $196

9. Replace Thermostat

What is it? It regulates engine coolant temperature to warm and cool to ideal operating temp.

What’s the damage? $225

8. Replace Evaporative Emissions Purge Control Valve

What is it? It also prevents fuel tank vapors from escaping into the atmosphere.

What’s the damage? $176

7. Spark Plugs and Spark Plug Wires

What is it? These ignite the car’s air/fuel ratio; misfires can reduce gas mileage and damage the catalytic converter.

What’s the damage? $342

6. Replace Ignition Coil

What is it? It helps the engine start and keep running; failure can affect other vehicle systems, such as the catalytic converter, and prevent starting.

What’s the damage? $243

5. Replace Mass Airflow Sensor

What is it? It meters the air coming into your car’s engine and determines how much fuel to inject into the engine; malfunction can reduce fuel economy by as much as 25 percent.

What’s the damage? $378

4. Tighten or Replace Fuel Cap

What is it? Oh, c’mon, you know what the fuel cap is!

What’s the damage? $17

3. Replace Ignition Coil and Spark Plugs

What is it? These components work together to help the engine start and keep running.

What’s the damage? $401

2. Replace Catalytic Converter

What is it? An exhaust system component that changes harmful gases like carbon monoxide and uncombusted hydrocarbons into water and carbon dioxide.

What’s the damage? $1,190

1. Replace Oxygen Sensor

What is it? It measures the amount of unburned oxygen in the exhaust and tells a car’s computer when there’s either too much or not enough fuel as compared with oxygen for ideal operation; failure can reduce fuel economy by as much as 40 percent and cause further damage to your car.

What’s the damage? $259

This year’s CarMD study also broke down the frequency of check engine light repairs by model year and found that model-year 2005 vehicles were most likely to need one or more such repairs. That should give U.S. car owners pause as the age of the average vehicle on the road rose once again to 11.6 years.

“While check engine issues can occur on any age vehicle at any time for many different reasons,” said David Rich, CarMD technical direct, in a statement, “this report reminds owners of 10- to 12-year-old vehicles to be vigilant with their maintenance routines and to be prepared for the possibility of a check engine light repair.”

Need to find a dealer for service? Go to Cars.com Service & Repair to find your local dealer.