That is freaky. Justin's tune should not impair reading codes.
A bad PCM causing bad engine running / loss of code retrieval - causing other issues to cascade?
As far as i know, Jason uses used/traded PCM's. They are expensive and that's fine.
This is not a knock against Jason, but I elected to keep my stock PCM as a spare just in case I have an issue like you are having.
This way if the truck acts the same after swapping the old one in I can rule out the PCM and look to other modules or wiring. If swapping solves the issue then I can send Justin's PCM back and still drive (although not nearly as much fun) until the problem is found.
I hope it turns out to be silly and cheap. I am a big fan of cheap.
