P20EE was common on the 14 EcoDiesels. They basically replaced all the 14's SCRs. Not saying that your SCR will be replaced, but it may need to be.
Now, what have you been running for DEF? Has it been sitting in the tank for long? I understand that the big trucks have smaller DEF tanks than the small trucks. If I am not traveling much, I will put a little in as needed. If I am traveling a lot, then I will fill up at the truck stop.
TV - 2015 Ram Truck EcoDiesel
TV - 2006 Jeep Liberty Turbo Diesel (Retired to Daily Driver)
TT - 2015 Rockwood Roo 183
Nights Camping --- 2015 - 19 Camped | Winterized -- 2014 -18
Come read my Camping Blogs