Yea i ran over a puddle and the mil light came on i checked it and its code 77 or 126 with the scan tool... the scan tool says bank 1 sensor 2... now witch sensor is it? i know its on the downstream but there are 2 downstream sensors.. please help a brother out!

 

According to what i've read here (I've also got a 77) the its the rear o2 sensor which is a backup sensor if the front 2 arent working. I still have not replaced mine because I cant figure out if its going to prologn the life of my car or if it just makes less pollution.