Find someone with an infrared hand held thermometer.
If both cats are about the same temperature after running a while, then the code is wrong. Some codes are "Systemic "codes that pop up for an indirect error and cause the dealer to rub their hands together gleefully while planning the route to the bank with your money
As said before, try changing both inlet and outlet O2 sensors first. Much cheaper than cats and do a lot to correct mixture for the cats combustion.
Thinking on it a moment I think that code could be generated by the after the cat O2 sensor failing in the new multi closed loop systems.