Since I have had my '11 Duramax, it has been to the dealership twice for the DEF system, and once to a private truck shop. The truck shop replaced both nox sensors and the entire DEF system 10,000 miles ago. Yesterday the service exhaust light, and the service engine light came on again! Codes read that the nox sensors are gone, and there is a problem with the DEF system!
Called the dealership where I bought the truck, and the service manager told me his diesel guy has no idea what is going on, and that I should continue to work with the private truck shop.
He says there is nothing the dealership can do, and that GM's technical bulletins do not address the issue
I am now in the process of having the truck shop eliminate the system!
My next stop will be a Ford dealership, thanks GM!