check engine light (o2 sensor)

[xgagne55x]

a few years back i had my check engine light come on and was told it was the 02 sensor. to cheap to fix it. light has continued to come on every few months for a few days then gone never worried. light has now been coming on 1 day the going off the next then back on. not sure of code for light need to get it checked and possibly spend money. what is the purpose of these o2 sensors i seem to get decent gas mileage (27 mpg) and have always passed the state inspection tests. any comments would be appreciated

[thaharlequin]

They tell the engine what the a/f mixture was and it adjusts accordingly. the light coming on and off mor often is probably the result of both of the sensors (one in each exhaust manifold) starting to go. The nice thing about having two banks/sensors is when one starts to go out your engine doesn't run like crap because the ecu can get info from the other bank. i had a dodge with just one sensor, and until the ecu picked up something was off and switched to open loop it ran like crap.

[ghettosled]

if your car runs too rich too often, you can also kill your catalytic converter. oxygen sensors are not too bad to replace in terms of cost. if youre looking to save a couple bucks, there are some generics you can splice in as well. though running 27mpg (i assume on a 4-cyclinder) isnt bad at all, but who knows. maybe you should be averaging 30mpg like i do on mine.