If one O2 sensor goes bad, would it just be wise to change both? I got a check engine light yesterday, so I took it to Autozone. The code came back as the O2 sensor, but I can't remember which one. It has 135,000 miles on it, and I have no clue if they've ever been changed as I just bought it. With one going bad now, my thought is that it's just a matter of time before the other one goes. Or, should I just go back to Autozone, figure out which one it is, and order than one?

 

yes, take it back and get the code. there is a different code for each 02 sensor. search obd codes here or on google. also, i wrote a tech writeup in the maintenance forum on changing out your 02 sensor

bob

 

I would just change the one that's gone, you're not saving much labour by replacing both now. Leave the one that's still working until it goes.

 

I've got the writeup and code list from here. I was able to find that. I just wasn't sure if it was common that one would go out followed by another.

 

The one before the cat often goes far more quickly than the one after the cat.
I would only replace the one that caused the code.

 

I had the same thing happen to my 97', but shortly after I had replaced it my check engine came back and I was having throttle problems. I pulled the code for bank one sensor one(the one I had just replaced). For some reason the Bosch style doesn't read o2 right; I swapped it out for Walker and by looking at them, they are two totally different styles. Everything is all go now and my baby is Runnin' strong.