That's certainly not normal. Is your truck doing regenerations? Have you ever had the EVIC message saying "DPF is 80% full - proceed safely to highway"?
The only time I've ever heard of the engine going into limp mode like that is if you ignore those EVIC messages and the DPF hits 100% full...then the dealer has to do a forced regen (or so I understand)...but that shouldn't happen if you follow the instructions.
The only time I've ever heard of the engine going into limp mode like that is if you ignore those EVIC messages and the DPF hits 100% full...then the dealer has to do a forced regen (or so I understand)...but that shouldn't happen if you follow the instructions.