I'm making assumptions also so no worries. I so believe there's some sort of sensor that gauges the purity or qaulity of the def because some people got the idea to add water instead and that didn't work out very well.
Truck is doing great! I love my lml. However, the rumor the trans can handle 550rwhp is false. Lol. Mine is hurting and is about to get a little shot in the arm so to speak... Haha. I will post some pics of its build shortly as I know the lml trans is a tuff nut to crack...