Oh I forgot to add - you'll see very different data on the pre-catalytic converter sensors than the post-cat sensors. The pre-cat will switch strongly and rapidly, the post-cat will be very laggy and look more like a "bad" sensor. That indicates the cat is doing its job and reducing the amount of oxygen (and with it, the unburned hydrocarbons) in the exhaust. If the cat has failed, the pattern will look like the pre-cat sensor.