The DEF freezes all the time. It's not like it sits there for a week with the heater on. The heater is just so it actually functions after driving for awhile and the def tank has a chance to thaw. There is no damage to anything for the DEF to be frozen, and continue to be frozen. You'll just have more NOx in your emissions.Its high 20s and the def heater is not functioning. The def heater needs replaced or maybe wiring i would think. If it gets into the teens and the def tank and lines freeze, serious issues will arise. We have been unable to get the 175 mile to safe mode to go off today. So we maybe driving alllll the way back home at 60 mph or less. We have a call in to a chevy diesel mechanic buddy so maybe he can help. But again, modern truck problems drastically alters multiple days of a hunt.
1) if you live in an area you can, delete.
2)Get a code reader than you can reset any code. And keep resetting it until you get home. This is mandatory with any modern diesel. The EPA would rather you die in the cold than you be able to drive a perfectly functioning vehicle home.