O2 sensor, bank 2, the one behind the catalytic converter, just as your BT tool said.
Got mine swapped out 2 yrs ago. Love the BT tool
There are 4 O2 sensors total (2 pre, 2 post catalytic converter). My mechanic didn't know which one was bank 1 or 2, so I had both swapped out, which fixed the problem. Labor's expensive in NorCal, and I didn't have time to consult my Bentley manual (since this was my only car at the time).