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If your "Check Engine" list is on, you’ll only wind up paying for bigger repairs and suffer a drop in fuel economy if you ignore it.

Here’s some good news for cash-strapped motorists: The average cost to repair a mechanical issue that’s indicated by the “check engine” light on a vehicle’s instrument panel dropped by 10 percent last year, now standing at $357 including parts ($216) and labor ($141).

That’s according to the 2018 Vehicle Health Index of check engine-related issues conducted by the auto repair website, based on an analysis of over 7 million reported repairs registered last year. We’re listing the 10 cheapest and costliest check engine-related fixes in the accompanying box.

Noted by either an outline of a car’s engine or the words themselves, when illuminated the check engine warning light commonly indicates a malfunction in either the ignition, fuel injection, or emissions control system. A technician can quickly analyze the problem by plugging a hand-held diagnostic device into a car’s OBD II port (it’s typically located under the dashboard) and retrieving a five-digit error code.

The five most common issues identified in the 2018 Vehicle Health Index are a faulty oxygen sensor (average cost to fix $238), ignition coil/spark plugs ($367), catalytic converter ($1,271), the fuel-filler cap ($26) and an EVAP purge control valve ($147 – this helps prevent fuel vapors in the fuel tank from escaping into the atmosphere).

Arguably the biggest check engine light problem is that, for many motorists, it’s just too easy to ignore, especially if the vehicle isn’t exhibiting any specific mechanical issues. Still, car-care experts urge motorists to have the underlying problem resolved in a timely manner, both to prevent what might be a simple fix from both becoming a much costlier repair, and to save money at the gas pump in the meantime.

 “As the summer driving season approaches and gas prices inch past $3 per gallon, CarMD reminds vehicle owners that when the check engine light is on, even if your car seems to be driving fine, it will suffer from reduced fuel economy,” explains the website’s technical director, David Rich. “It’s important to have it looked at as soon as possible — especially if the check engine light is blinking, which can indicate a serious problem.” 

Of course, local prevailing wage rates can greatly affect the cost of any vehicular repairs. According to CarMD, those living in the Northeast U.S. pay the most for check engine repairs at an average $367, while motorists in southern and western states enjoy the most affordable rates at (an only nominally less costly) $358.