With a P2A04 readout on my 2006 gmc 1500,how do i know which of the two 02 sensors to replace?

Question

need to know which sensor to replace

Answer 1

P2A04 H02S performance Bank 2 Sensor 2

Bank 1 is always where cylinder 1 is located, the other side is Bank 2, Sensor 1 are the upstream , what you set is for Sensor 2 this is the downstream or the catalytic monitor sensor. in this diagram it is number 9 or 10