Muzna

Can someone please explain to me what the oxygen sensor in a vehicle does?

Spock

Good thing I didnt sleep through Thermodynamics 101 during freshman engineering In a combustion engine, it is imperative that the air to fuel ratio be monitored and controlled, the latter which is done through manifold fuel injection systems in modern cars. A close loop feedback system, where the O2 sensor provides the feedback (coupled with some other sources on board the vehicle). So basically the sensor tells your car's on board computer (PCM) how to adjust this ratio.

If your sensors bad, please get it changed, i) because your car might fail an emissions test if required OR the engine might misfire during heavier loads. Your check engine light should be on if the sensors kaput.

Muzna

okay...so that's exactly what happened......engine light is on....failed emission test....guy said we may need to replace sensor.....I said okay do it.

guy calls and says that it doesn't appear to be sensor cuz the light is related to some other O2 sensor (which I find confusing....cuz how many could there be?) so he's checking plugs and they may be the culprit.....

maroush

For a second there, i thought you were talking about the oxygen sensors in military jets.....

queer

he probably means the check engine light's error code (shows up when your car is hooked up to a tiny computer thingie) doesn't correspond to the oxygen sensors. he shouldn't have to go to much trouble to find the offending component though, its a simple table look up from the repair manual.

Muzna

okay....so can you now explain to me how the O2 sensor and the catalytic converter are related?

what does the catalytic converter actually do?

Spock

A cc is just a device that is environment friendly and produces some chemical reactions by which the toxic products of your exhaust combustion are broken down to less harmful substances so that the air you and I breath is cleaner. It doesn't impair the cars operation in any way, though again your car might fail the emissions test (I live in a state where we dont need to do it)...

That guy diagnosing your car, I wonder what type of OBD2 reader (the device used to connect to the car and read codes) because the codes for the O2 sensor and the cat conv are different. Sometimes they put a second O2 sensor after the Cconv, because of they are showing the same O2 proportion, that means your converters not working right. Thats when your light turns on and the code should correspond to bad cat converter. So in short, you should ask him what code the car is spitting out for the check engine light exactly and what it corresponds to because it would really suck if you get something changed, which really wasnt malfunctioning in the first place.