Ahh ok, I was assuming you were replacing the OEM HU functions with the yumcha.
Splicing in to pin 11 (brown) might work. See below:
http://img24.imageshack.us/img24/557...elcontrols.jpg
Removed wrong advice...
Let me try that again (I had a big night last night)...
The BRN wire is tied to ground, so the voltage drop must be read from the GRN/RED wire. (It's been a while since I installed my G4, so I can't remember which color wire I used, but it must have been the GRN/RED wire).
It's really one of those "try at your own risk" things, but theoretically, it should work.
-Steve
PS. The yumcha HU (like my G4) will need to be "trained" to map buttons to functions.