Now I'll have to try and find out which pinouts are for mute.

Great information !!

 

I am pretty sure you can induce a mute by using pin #24.
Whether it needs to be grounded or sent high, i do not know.

I got those pinouts directly from the Bose head unit when I took it apart once.
I am most interested in seeing how the CD-R/L +/- lines can be used.
Those are audio inputs for the CD Changer's Right and Left signals.
Figuring out how to work that would allow people to run line in audio into the Bose...VERY USEFUL!
However, it may not be possible at all: when I had the head unit opened up I noticed a few missing components!

Pv

 

Here is a pic of the rear of the Australian Bose system which seems to have a connector blocked off (sorry for poor quality)
We dont get Nav option here.

 

Weird! It looks like you are screwed then!

Pv

 

Here is the rear of amp

 

We get screwed for everything....thats why we live "DownUnder"

 

You definitely can mute the radio using pin 24 with a "high" (5 volt) signal. If you connect your car kit to the nav input lines, the sound will come through your front speakers and the rear speakers will mute.

You could do this even if you don't have navigation. The harness goes to the head unit.

The cool thing is, if you use the factory mute option, the automatic volume adjustment still occurs for the cell phone.