Last year after towing across country and returning home, the very next day after driving without trailer 10 miles to the store upon restart at the store a warning "Service DEF System" and check engine light came on. Took to local dealer and was advised I may have used bad DEF fluid, they reset the light and it has been fine for 10000 miles. Well we just got back from another week long towing the camper trip and it happened again. Drove to the store and after coming out of the store and restarting the same warning came on. I have only been using quality DEF fluid and not the pump stuff as recommended by the dealer. I just made an appointment with the dealer. I hope they have a bulletin or fix for it this time. Anyone with similar issues?