hello i was wondering what the o2 sensors on a 2001 Chevy silverado 4.8L should be reading at. My front 2 are bouncing from 100 too 900mvs and my left rear is at about 550mv and right rear is running at about 90 mv. I think my right rear needs to be changed because my trucks gas mileage has gotten worse then when i first bought my truck. If anyone could help me with this it would be greatly appreciated.

 

The front O2 sensors are used for fuel control not the rear. The front sensors are working as they should. The rear sensors are used to monitor the converters and that is about it. They should always be lower the the front if they cats are working properly. Is the check engine light on? How much worse? How old was it when you bought it? What is your current gas mileage?

 

I bought it a year ago my check engine light isnt on but i did just replace the catalytic converters because one was plugged. I used to get about 19-20 mpg and now i get about 15 mpg. Should the one o2 sensor be that low?

 

Is that the side with the new converter? The side with the new converter will be much lower.

 

they are both new they are part of the y pipe.