I read this thread before pulling my travel trailer across the state. Bought my truck two weeks ago, and it is a 2014, that supposedly got lost in paperwork, and sat on the lot for a long time before being put up for sale.
After hearing about DEF, and reading some of your input, I decided to run the DEF out as far as possible, as I have no idea how old the stuff in the tank was.
Tank wasn't completely full, but probably close. I drove 1600 miles (1200 was with a travel trailer, and exhaust brake on full) before the "low DEF" light came on
Reading the manual, I should get a "low def" message when there is about 300 miles left. At some point a mileage countdown pops up, then you are limited to 5mph, and have "see dealer" messages.
I got the "low def" message, and within 15 miles, a see dealer message popped up. I was hoping to use a little more before filling it, but got worried when I saw the dealer message, so I pulled over poured the 2.5 gallon box in.
Does the "see dealer" message always come up at that point, or is something else wrong? All messages went away after I poured the box in.