In 2019, for the first time since CarMD has reported on these rankings, “replace catalytic converter” was the most common check engine light repair. Catalytic converters are costly repairs that don’t typically fail unless maintenance and other repairs are ignored, or a vehicle is up there in age. This can be partially explained by the trend up in average vehicle age from 11.7 years in 2018 to 11.8 years in 2019. Back in 2010 when CarMD first started publishing Vehicle Health Index data, the average vehicle age was 10.6 years old. As people keep their cars and trucks longer, the automotive aftermarket will need to adjust related parts forecasts accordingly.