O/T Help with my 1996 Taurus 3.0

I scanned the car and this code:

o2 sensor second bank I replaced the two o2 sensors in the cross over pipe, but the same code came back after it was cleared. Does anybody know how many o2 sensors total there are? Maybe there are more than two sensors? If there are only these two sensors i wonder why the code came back? Any ideas?

Thanks all help is appreciated

Fast50hz