It most certainly has not been that cold. My garage was about 68 while outside might have been in the low 60's. I suspect it is an ECU or circuit issue and not an actual temperature or heater problem.
Wonder what temp that heater comes on at anyway?
If I am ever going to do a mod to this car it will be to defeat the DEF system. It causes nothing but problems and error codes best I can tell.
2010 Black 335D Sport/Premium, Michelin PSS 235/265
2000 Silver Z3 3.0i (Ret)
1999 Silver R1200C (Ret)
1968 Black 1600 Coupe (Ret)