The oxygen sensor

An ingenious part of your car's emission control system is a device called the oxygen sensor, the O2 sensor. The term precisely describes what it's supposed to do: sense the oxygen content in the exhaust gas coming from the engine. On some vehicles there may be two or more of them.

When emissions are excessive, the O2 sensor will signal the engine management computers to change the fuel - air mixture or to perform other engine adjustments to reduce emissions. Because this instrument, about the size and shape of a spark plug, sits in the flow of exhaust, it's vulnerable to heat and chemical attack.

Eventually it could fail, so it should be checked as part of a performance diagnosis. When the results so indicate, the O2 sensor should be replaced to avoid deteriorating performance and high emissions. Not only does a properly operating emissions control system help clean up the atmosphere, it also improves engine performance and economy. However, says the Car Care Council, even the best mechanism can compensate only so much for neglected maintenance. Components like dirty air filters or worn spark plugs can make serious trouble for the system. You'll notice the difference in the air and in your wallet.

For more maintenance tips log on www.carcarecouncil.org.