X5 display shows Ext. Temp -37 degrees and fuel gauge is innacurate

[X5H]

Hi,

This morning whilst trying to find the BT code in the trunk I noticed that when i tried to start the X5 it took abit longer and the message Ext. Temp -37 degrees(Its not that cold outside!) is displayed. Ive also noticed that the fuel gauge isnt accurate as it shows about a quarter of a tank but I only filled it up yesterday. No visible leaks as far as I can see. I also saw the message Transmition Failsafe something although the gear changes are fine. I did a search on here and it pointed to a potential problem with the battery. Ive had the battery checked and its showing 12.4volts. The car was stood for about 3 weeks and the battery was charged to get it going. Ive been driving it around for a week now but only today have I had a problem

I dont get the transmition failsafe message but do still get the Ext Temp -37 degrees and the fuel gauge is still innacurate. Car seems to start fine.

Any ideas what the problem could be here and how I go about getting it fixed please? Is it worth putting the battery on charge and is there a way of resetting the fuel gauge/outside temp control?

Thanks in advance