NEW INFO:
I found this diagram:
https://5series.net/forums/e60-e61-p...s-jump-152311/
It shows the CCC & the X13812 with pin#10 BLK/VIO, going all the way across, but does not show where it terminates.
Can someone please chime in and solve this riddle?
PS.
These guys managed to use the 'Phone Mute' pin in BMW e46 2002. (not CCC but similar concept)
https://www.rdforum.org/threads/6542/