02 Pathfinder "Check Engine Light"
 

I recently changed an o2 sensor on my 02' Pathfinder and about 1 month later my check engine light came on again. I believe the 1st time it was supposed 2 be bank1 sensor 2 which i believe is on the downstream after the 1st catalytic. Now my buddy scanned it & it says bank 2 sensor 2. Im not sure which side bank 1&2 are. I believe bank1 is Driver side&bank2 is pass. when looking 4m front of vehicle. Any help with this matter would b greatly appreciated. THANXS.