So if I understand you correctly the cat drives correctly in the bypass mode? I had to replace a drive card on my PB200D after driving a whole season in the bypass mode. The dealership replaced the analog one with a digital one on my PB260D even though that turned out not to be the problem. I have my old analog one which may work on your PB240D.
If you haven't already done so I would get ahold of Pisten Bully Tech services in Reno. I have their number some where if you can't find it by googling. The tech guys will walk you through a reset and email you the info you need to trouble shoot your cat.
Hey Travis,
Did you find the cause?
. Rev. . Havent got that one it still works you need to turn to the right.