Well, i hooked my truck up to a scanner because of such bad mileage. and the o2 sensor in bank 1 section 2 or side 2 whatever it is called, had no voltage at all, which is the downstream o2. The check engine light is not on, and I was wondering if I should replace it or not? I also had a lazy o2 sensor which was replaced, and i was told that the downstream o2 sensor will not effect my mileage at all. What is your guys opinion? Thanks

 

if you know its faulting i would replace it

 

Correct. The downstream sensor monitors cat efficiency only and has no effect on the air/fuel ratio.

 

well if it is not necessary im not going to spend the extra 50 dollars, i am not sure what I will do yet, i dont have alot of $ at the moment, and it is not throwing a code or anything