Your car had an independent telematic unit fitted, so the microphone link would of gone directly to that unit and from there to the Head unit.
I've just re-visited this topic so you do have the independent telematic unit fitted but not not the hands free telephone interface.
It is item (3) in this diagram:
The independent telematic unit has these buttons on the front fascia
To get to it, you'll have to Unclip and detach the independent telematic unit control panel (1) (at "a") using trim removal tools.
Disconnect the connector of the independent telematic unit control panel (1).
Remove the independent telematic unit control panel (1).
You'll need to remove the glove box and the Audio Head unit. There is a mounting case to protect the unit (it is linked to the airbag control unit so be careful). Remove the bolt (2).
Unclip and detach the independent telematic unit support (3) (at "b"). But also remove the Fascia emergency call and service button unit.
This is what the unit looks like:
This is the 18 way black connector So the microphone enters this unit first of all via Pins 1 & 10 and exits through pins 2 & 11 to the connector at the back of the Head unit. But - as you didn't have the hands free kit or RD45, you'll need to trace back the wires from there on pins 2 & 11 to see where they exit.
KEY
Channel number | Allocation of channels of connector |
1 | Microphone signal input (+) |
2 | Microphone signal output (+) |
3 | Not connected |
4 | Emergency call button warning lamp supply (orange) |
5 | Impact information |
6 | Emergency call button warning lamp supply (green) |
7 | Warning lamps earth |
8 | Reception of the debugging signal |
9 | High Speed Comfort CAN |
10 | Microphone signal input (-) |
11 | Microphone signal output (-) |
12 | Not connected |
13 | Signal from the emergency call button |
14 | Supply |
15 | Signal from the assistance call button |
16 | Earth |
17 | Emission of the debugging signal |
18 | Low Speed Comfort CAN |