I've seen where folks let their DEF get low and got an 800 or 500 mile range warning. I had better than a half tank of DEF when I got a 500 mile range warning. Just to be sure, I got a 2 1/2 gallon container and started pouring it in. After about 2/3 of the DEF went in, the tank was full. Cranked the truck and I still have the warning. Now I'm down to 463 miles. I have about 265 miles that I need to drive tomorrow while pulling a 16,500 Lb 5th wheel camper. Will the count down be the same as not towing? Any way that I can fool the computer, like puling battery cables for 5 minutes?