[EagleDriver]

My 2004 spit out the p0136 code a couple of months ago, which is for the bank 1 sensor 2 Oxygen Sensor. I went to NAPA and bought a replacement sensor (Bosch). However, the light came back on after about 20 miles of driving, so i figured the sensor was not the problem, so i put the original one back on. I then took it to a local mechanic who had a detailed diagnostic, which read the output voltage of the sensor.... 0 volts, nothing. So now I am wondering how to fix the problem. Specifically, i am wondering...

A) if the ECU is not getting any voltage return from the sensor, then its probably a wiring issue?

b.) If i bring this to the dealer, should this be under warranty (55K miles on 4runner). I am wondering if the problem is not the 02 sensor itself, but somewhere in between does this qualify for the 8yr/80K emissions warranty

C.) What are the chances of the problem in fact being a bad 02 sensor (also, the replacement one being bad).