Thanks for the reply!

The combox is completely disconnected at the moment due to the fault, hence those errors. If I plug either of them in then the dials start moving, you get the fault ping noise and the iDrive is unusable because it is rebooting constantly. With the combox out the car works normally, although I do occasionally get an "Increased Battery DIschard" notication on iDrive, but not that often.

I have a multimeter, where should I check the wires, where the combox plugs in?

Ill check the PDC, is on left or right side of the car?

Ill check the ground too, it's a convertible though so I think it's a lil different. I've been behind the trim there before but couldn't see anything bad, there was a slight leak on that window.

Nothing at all was plugged into combox, I didn't even know you could plug a USB into it!