The same problem occurred today with my 820D but the solution is likely not applicable to most. I live on the outskirts of Winterpeg (Winnipeg, Manitoba) and when the grill was plugged in this afternoon, temperature was -24 degrees C (about -11 F) and got the ERR error code (today was the lowest temperature using this grill). Referred to the manual and after checking the connections and plugging back in with no success, decided to try something different. I unplugged the grill, heated up the grill probe for a few seconds with a propane torch, plugged the grill back in, and received the ERH error code (grill overheated). Unplugged the grill again, let the probe cool down a bit, and when the grill was plugged back in, it worked normally.