Where is the bank one O2 sensor located on a 1998 Toyota4Runner?

bank 1 is the engine side that has number 1 cylinder.

Depends on which engine you have! 4 or 6 cyl.???? V6 pass. side is bank 1, 4 cyl only one bank so it is #1. Now, is it sensor bank one sensor 1 or bank 1 sensor 2?? We need the actual code number(s).