So, I had a recent 0420 code re-appearing. Replaced the cat. Was about to try the spark plug non-fouler trick in the rear 02 sensor because even after the cat replacement, it still threw the 0420. (03 Ram w/ longtubes and superchips). So before I go to put on the non-fouler, I go to clear the code with SC. So, I plug it up and it says 'No DTCs exist'.... then 'Do you want to clear DTCs'. So I hit 'Yes' because I have a CEL on. So after its done, I unplug and start the truck and it is still there? I do the same thing over again...'No DTCs exist' and 'Yes' to clear the CEL. Still there... I have no idea whats up? Anyone want to chime in and help me out?