ISB6.7 DEF HELP

[JimT]

(01-20-2021 )lastmanstandin31 Wrote:  Problem is def system will not prime half the time and throws pressure codes and def input line codes every day which derates the truck. I

Sounds like you know where the problem lies, it's just a matter of going over those parts until you find the cause. Either the pump isn't doing it's job or there's a line or fitting leaking. Also, double check the filter. it's really easy to NOT get it seated properly and therefore the cover won't seal properly.

When you say you replaced "doser unit" do you mean the doser valve mounted to the decomp tube or are you referring to the pumping unit? What about sensors in the DEF system? Maybe a bad pressure sensor? If someone put paint in there I'd be suspicious of any rubber seal or o-ring. Could also be something inside the DEF tank itself.