O2 Sensor Question

i think my O2 sensor is bad becuz i smell a foul oder when the car is on sometimes.. also how do i know which one to change and how do i go about changing it... also how much does one go for? thanks for any info

u have 2 o2 sensors, one on header and one behind the catalyc converter.if it was bad ur check engine light would come on. Change ur oil, wash ur car, and clean ur engine, if something was spilt on ur engine and burnz it can reak prettty bad, if u have a manual it might be ur clutch burning out and stinking like hot garbage. its not ur exhaust cause ur 02 sensor would cailibrate the ecu to add and subtract fuel and what not. If it cannot due to spark plugz, low burning oil or whatever then ur check engine light comes on..... have nice day...

the secondary o2 sensor has nothing to do with your fuel corrections whatsoever. in an obd 2 car it is there almost strictly for emissions monitering of the catylitic convertor. if the catylist were to break down or become clogged it would trigger a check engine light to let you know that your emissions control devices are not functioning properly and you are in violation of federally mandated emissions laws and must get it fixed imediatly. secondary o2 sensor failure will not throw you into a limp home mode, only primary o2 sensor failure will. the secondary o2 sensor will not trigger a check engine light untill the return to the ecu has reached an unacceptable level. since it must equate for many different variables of combustion there is a range of voltage that is returned that is considered acceptable. if your catylitic convertor is taking a shit on you it may not have reached a level yet that put the voltage return outside of acceptable standards. the sensor may send back different voltage but the ecu only reads it against its preset voltage parameters and does as simple boolean answer, true or false.

but before you start replacing your cat do what had allready been mentioned and check for leaks that may be burning off and creating your smell.

thanks for the info. but i've heard that if i change the o2, since my car has 100k, that it will get better gas milage or sumting.. is that true?

Originally posted by m3kidds
thanks for the info. but i've heard that if i change the o2, since my car has 100k, that it will get better gas milage or sumting.. is that true?

maybe if the primary sensor is worn enough, but remember the are usually around 200-300$ depending on the car.

actually i got some hook ups so it will be far less.. how hard is it to change? i just see the one in the engine bay and it just has like one wire on it.. is that all?

My car is messed up, and the genius I took it two said my O2 sensor was not reading properly, and it needed replaced. I found one for $185, and it fixed not a damn thing. I had the guy put it in though, he only charged me like $20 so it can't be hard.