Sorry, I missed your post until now.
I'm looking for the particular spot in the wiring schematic but to start with there's a connector in the vicinity of the steering column that has about 6 cavities (but less wires IIRC) and the audio mute for telephone wire is PURPLE with orange stripe. I'll do more digging shortly.
Edit: Purple with Orange stripe (PO)
Further edit: From the WSM...
Where a telephone is installed, signals are input to the head unit from the
accessory power connector. When the telephone is active, a mute signal is
input on a PO wire. The telephone circuit positive is input on an SO wire and
the telephone circuit negative is input on a YG wire.
5 wires in the connector,
Purple with orange stripe (cavity 6),
slate with orange stripe,
yellow with green stripe,
green with white stripe,
pink

