How often should they be replaced? Are they good until the check engine light comes on? I'm thinking they should be replaced at around 30k miles.
I've got about 70k one the front 2, which are Bosch....and the cat o2 sensor is original....so it's got about 170k on it
Seems like the performance isn't there anymore, and seems like my mpg is down too from when the car was new....
Thanks for any info......I'm trying to figure out if I should just order 3 new NTK sensors

 

The life expectancy of an O2 cant really be put into time. Unless you are getting a code for any of them, don't worry about changing them.

 

Will the cat 02 throw a fault code? I know the front two do...but wasn't sure about the rear one.

 

QUICK QUESTION, WHERE ARE THE 2 O2 SENSORS, BEACAUSE ONE OF MY SENSORS IS BAD AND ITS MAKING MY CAR RUN LEAN?

 

80K is the life of the sensors. Even if they don't thro a code, they get lazy screwing up fuel/air ratio. Change it and recover the cost of sensors with better MPG.

 

Thats what I was thinking.......seems like I read it somewhere. I think it was in my S12 FSM, and it said to replace every 60k or so. I think I'll go ahead and order 3 new NTK ones......thanks