Pardon my rudeness but are you absolutely certain the O2 sensor has failed and it is not a broken wire to the O2 sensor. I had one of those and I did not check the wires before I replaced the sensor for the first time. A connector was rubbing on the damper of the right drive axel and wore a hole in the insulation an through the wire. This was after a front engine mount failure which allowed the engine to rotate slightly and tug the the wire harness close into the axel. Neat problem. I fixed my O2 sensor problem by replacing my front engine mount.