Just had to replace both batteries due to cold weather and age. Now the problem, the DEF fluid tank warning has now come on and I took back to dealer and they said @#500 to repair. Something about the plastic junction box over the firewall battery has caused problems with system. Oddly enough they replaced the def heater this time last year, I just don't see how replacing the batteries caused this problem, any ideas or problems others have had? Let me know!!