o2 sensor for pontiac bonneville 96

??? well your have a v6 motor so you have two banks

I'm assuming a scan tool is telling you that you have a problem with o2 sensor bank 1 sens 1 or bank 2 sens 1 I forget which is exactly bank one but its were the number 1 cylinder is (follor the spark wire on coil that says one to plug)

2 banks on these, most of the time the first bank needs to be replaced