DEF light flashing

I drove a 2012 kW 660 with a past company and it was a complete nightmare with the def system.

 

With a Cummings emission engine it could be 1 of 1000 different things, take it to the dealer so they can start throwing parts at it, $5000-$20,000 later, it might be fixed, just the reality of these engines.

 

You well need to take to the shop an clear the codes out of it because that is what mine is doing an even when it is very cold.