There is one after the CAT.

All 96+ vehicles have an O2 sensor after or in the exhaust manifold. A V6/8 has one in each manifold (bank 1 & 2). They also have and one after the catalytic converter. If the engine has two CATs you have a sensor after each of them (sensor 1 & 2). Thus the nomenclature of the bank 1 sensor 1, bank 2 sensor 1, etc.