Reviving this thread.Probably a late and maybe unnecessary response, but I had the same issue after the 12V battery was completely drained. I lost GPS, internet and eCall functionality. The solution was taking out fuse 26 in the fuse box under the glove compartiment and putting it back in. GPS and internet immediately came back; eCall came back after driving a few km.
So the statement that the TCAM module has its own battery backup and can't be reset by taking out te fuse seems to be incorrect, at least in my case.