Fiat don't use adblue, they fitted a bit in the engine to send the gases round again. This failed on lots of motorhomes and was subject of a recall, plenty of posts about this from funsters last year. Look for egr valve threads
Some Ducatos actually do use adblue, although none of the particular base units find their way into motorhomes, as far as I know. I only know this because I was surprised to find mention of adblue in my manual. I think it is certain crew cab units or some such.