I just got the fill DEF tank message up.
Jags info isn't too forthcoming.
it states that there are 3 warnings -
fill
x miles left before no starts and
no start
it then states that it takes 2x 1.9 liter bottles before it will start again from a no start message but no info on how much to put in from the first warning.
the DEF level in the menu simply tells you how many miles left, i wonder what a full tank is?
the capacities section state that the tank holds 17 liters...
the workshop manual (which i just got last night) also covers what to do in sub -10 climates get her warm as the def can freeze at these temps, sort it out and it may take a day or 2 to correct sort of thing.
I didnt get a chance to play with my diag tool to see if there is live dat on an actual level, bu ti might just stick in the 2 liters to clear the message until its next service.