it only has one cylinder bank but 2 sensors, one precat and one post cat - the post one is for emmissions purposes only. the pre one is for ECU fuel trim.
If you plot a graph of the precat one it should show wave form as the sensor voltage spikes up and down due to the firing strokes, the rear one is usually reading steady.
I have a tool that maps this - it really helps in diagnosing problems. Infact most nicer OBD scanners have this function. the Torque app in android also has this.