For the 2.5L V6: the rear upper sensor is not THAT hard to replace. Bank 1 is the rear bank, and P1131 means the upper sensor, before the cat. The rear upper 02 sensor is definitely the hardest of all 4 sensors to replace but it is doable. Having wrists that aren't fat helps
.
I worked from above and below to get access to that little bugger. There is no need to get in through the wheel well. As a matter of fact, going in through the wheel well will never get you near the sensor.
Anyway, when I did mine, I used the following tools:
misc sockets to remove coil packs
7/8" combo wrench (box end + open end)
Liquid wrench to loosen old sensor
There is a special 02 sensor socket out there but I did not use it.
That's all that comes to mind right now, but there may have been other standard tools used along the way.
For detailed instructions, do a search on '02 sensor replacement'. Someone out there wrote a detailed guide....
