Ok, my roomate and i (its good living with a EE) went out to the car and played with it till we figured it out. So here you guys go..
the colors are arbitrary for reference to pins only
Pin 1 (red): Right Channel Audio
Pin 2 (green) : Left Channel Audio
Pin 3 (black) : Audio Ground
Pin 4 : not used
Pin 5 (brown): Connect To Pin 6
Pin 6 (brown): Connect To Pin 5
It appears that you do not need to use a resistor between pin 6 and pin 5, we started off using one and it fell out, so we put a regular piece of solid core wire in and it worked just as well.
Update:
At the back of HU you will find the 20pin connector (second one from the right). The pins are ordered as following
1........10
11......20
There you go (the pin# in parenthesis is the pin# defined by ethlar post#1)
B3 = AUX SGND (3)
B4 = AUX SH GND (4??)
B5 = AUX GND (5)
B13 = AUX L (2)
B14 = AUX R (1)
B15 = AUX DET (6)
UPDATE:
Thanks to Chok for figuring this out, non US models that do not have the aux input option
Here you go