I'm having alot of trouble with a def system at the moment. Regen wont go past 600F. Dosing valve doesnt seem to be engaging. Only faults that show 3, with one going back and forth. 2 faults are the egr shutoff and protection. And the last one alternates between fuel shutoff valve- data erratic and then next time around it will be DOC undetected. Hoping y'all can shoot me some ideas.