Virtually every vehicle manufactured since 1980 has an oxygen sensor, according to HowStuffWorks. Most cars on the road actually have between two and four sensors, according to John Nielsen, the director of engineering for the American Automobile Association, as reported in an article on Edmunds.com.
HowStuffWorks also points out that the oxygen sensor measures the amount of oxygen in the exhaust system, which allows the engine to adjust the amount of fuel being burned. This ensures the engine runs at its maximum efficiency. In vehicles with an oxygen sensor, a malfunctioning oxygen sensor is the most common cause of the Check Engine light turning on, according to Edmunds.com.