I’m getting the P0420 code randomly. I reset it and sometimes it takes a couple days to come back, other times it’s a few minutes. I recently installed a Range Technology AFM/DFM disabled which completely stopped the engine code from coming back. I was curious this morning and unplugged the disabler to see if the code would come back and it did within an hour of my commute. This makes me think it’s not the catalytic converter but possible an issue when the truck switches down to 4 cylinders. Anyone come across this issue and know of a fix? Thanks!
