According to the annual CarMD® Vehicle Health Index™ one of the most common check engine light repairs is replacing the oxygen sensor. This relatively minor repair can be costly if neglected, leading to as much as 40 percent lower fuel efficiency, causing further damage to your vehicle’s exhaust system and adversely impacting the environment.

“Vehicles with faulty oxygen sensors typically seem to drive and handle well, but the malfunction can dramatically decrease fuel efficiency and lead to costlier repairs if ignored,” said Rich White, executive director, Car Care Council. “A faulty oxygen sensor means your vehicle is emitting more pollutants and if the check engine light is illuminated, it may not pass vehicle emissions testing in those states requiring it for vehicle registration.”

A vehicle’s oxygen sensors are mounted in the exhaust system; they monitor the catalytic convertor’s operation and the level of oxygen in exhaust gases to maintain efficient engine operation. The best way to prevent an oxygen sensor failure is to follow a regular service schedule, including routine oil changes.

Unlike the past nine years of the annual CarMD report, costly catalytic converter replacement edged out O2 sensor replacement as the most common check engine light repair. Catalytic converters do not typically fail unless maintenance and other repairs are ignored or the vehicle is older. Average vehicle age has increased from 10.6 years to 11.7 years over the past decade, contributing to this outcome.