Temp sensor reading?

My external temp sensor reading has started reading between -16 and -17.5 degrees!!! When I first switch ignition on it reads about zero which is what i would expect but then within a minute falls right down. A week or so ago i was looking through the menus on the climate control getting it to display true speed, I am not sure if this is related or not, is it possible to change to temp dispaly via these menus??

Thanks in advance for your help.