Up stream o2 Oxygen sensor above 3 volts?

[ojeysky]

Originally Posted by Yangs

I test and replace o2 sensor before on other cars but this time with my Yaris I have a very bizarre situation. While the car is fully warm in operation temperature According to my multimeter, it show's little above 3.00 volts and it doesn't fluctuate from 0 volt to 3.00..."a steady voltage" I try to give it some gas but it still doesn't fluctuate. What's very strange is that the instrument cluster does NOT throw any trouble code and even thou I stick in a diagnostic scan tool it doesn't show any trouble code and emission status are good. Not to mention MY GAS MILEAGE WENT GARBAGE!!! I never heard 3 volts before on a o2 sensor. Maybe Toyota did some thing different from other car manufactures or maybe I have a bad o2 or a short some where?

Also the down stream o2 sensor read 0 volts at idle.

Am seeing this same reading on my scanner. The upstream sensor reads between 3 and 3.3 while downstream reads between 0 and 0.9. From what I read here it seem it's a normal behavior? as I had thought both were supposed to read between 0 and 0.9 so I was quite concerned as well.

Thanks