This is probably why your 'Check Engine' light is on
Fox News
Problems with catalytic converters are the most common issues that caused Check Engine Light alerts in cars last year and came with a hefty repair bill.
The overall average repair cost for a Check Engine light issue was $393, an increase of 3.6% from 2020 and 2016 model year cars had the highest average at $397.87. The light is set off by a variety of faults throughout the engine and exhaust systems that can effect performance, fuel economy and emissions, and requires an electronic diagnosis to determine exactly what's wrong.
Engine oxygen sensors were second on the list followed by ignition coils/spark plugs, mass air flow sensors and loose fuel caps, the last of which cost just $24.77 for those who needed a new cap and didn't just have to tighten it properly.