Had the DEF 500 mile warning come on last week. Second time for this. First time early on when it was new. Put a 2 1/2 gal. container of Blue DEF then and all was well. This time I did the same thing but keep getting the 500 mile warning afterwards. Cancelled the warning a couple of times , and now I am getting a warning that I have 378 miles left on the DEF fluid remaining.
Its like the truck didn't recognize me adding the 2 1/2 gal. Anyone hear of this before ? Also the check eng. light is on now. Thinking thats related. 7,000 mile on truck

 

I had this exact problem in my 2014. I was on a road trip and the 500 mile warning came on. I put 2-one gallon DEF's in and continued down the hwy. Well, the light never went off! So I knew I had the DEF in there, and my DTE(limp mode) was just far enough out I would be home. The next day I went and got a 2.5 DEF and dumped it in, light went off. Told my dealer, they said it takes obviously more than 2 gallons to reset the system.
So next time, you have to dump 2-2.5 DEF's in, then have the last little bit splash all over the ground and your feet. I chalked it up as just another annoying modern diesel issue.

 

i had to reset the DEF once in the information center. It is just like resetting the oil when you change it. To avoid spilling DEF on the ground go to the dealer and get the Ford DEF filler tube. it's better than the one that comes with the box. The Ford one snaps into the DEF fill hole. If I do spill DEF on my truck I wash it off as soon as I can. That stuff is nasty.

 

Picked up another 2 1/2 container of Blue DEF and managed to stuff most of it in, maybe 2 gal.. Stopped before I made a mess. I had to cycle the key twice before the Low Def warning
went away. Didn't wait any longer this time to add the same amount as the last time , when the warning first came on.
So, if the DEF tank capacity is 5 gal. I can add 4 1/2 gal. 100 miles after I see the first 500 mile warning. I will look into the Ford fill tube that some of you say eliminates spills.
Thanks