Cascadia egr fault code problem

That is VERY rare. In 15 years of full time wrenching I can count on 1 hand the number of failed ECM's I've changed.

 

What the doser injector to do with egr system?

 

Aka 7th injector. Solves some issues before you get to the bigger $$ buggers issues. (EX. Inlet nox sensors, outlet nox sensors) It helps shoot fuel when your engine rpms ramp up the exhaust temps passive regen approx 600degrees active or parked regen1000~1100 degrees engine ramp up to burn along with the exhaust gas thats going to and thru aftertreatment device regen active or parked 1000~1100 degrees plus or passive 600 degrees to burn soot it's located after turbo and before the one box... dd15 watching my readings on laptop w/ dddl software, on high idle for approx 1hr Worth of fuel, again. Part of trucking that is not a good experience the 1st time and still i forgot how many times now.