Recently I tried a different form of Bluetooth hacking, I purchased a simple car kit and wanted to install it myself. Alongside the kit itself I also purchased the required vehicle specific cable to sit between the vehicle wiring and the radio and connect in the Parrot loom. However I soon realised that it was going to be more difficult than originally anticipated because there wasn't enough space behind the dash to accomodate all the bulky connectors, relaybox and oceans of cables. There were two issues, the adaptor cable passed through every single cable from the vehicle connector even though only a select few were actually used, the inline ISO connectors are rather chunky, the radio itself supports a phone input and mute trigger and so it seemed unnecessary to have the parrot amplify the audio and output it directly to the speakers.
So I set about looking at what was happening before the relay box and was able to determine the pinouts on the Parrot unit itself. The next stage was to simplify the adapter cable to remove unnecessary passthrough wires and remove the inline ISO connectors. I had to directly solder in Power, Earth and Mute wires from the Parrot and connect up the mono phone input to the "raw" output from the Parrot. The only additional wiring required was vehicle specific as there isn't an ignition switched power into the radio as it uses the CAN bus to change state. So I ran the ignition line for the Parrot into the connector with the vehicles cigar ligher socket (on some cars this is permanently powered on mine it's only on with the ignition). I was then able to mount the Parrot box behind the dashboard and route all the wiring behind the vehicle trim. Using this approach has the added benefit of supporting the external volume adjustment through the radio (and hence steering wheel controls). For reference the pin out for the Parrot CK3000 Evolution is as below (Other Parrot models use rather different plugs so I doubt it's transferrable).
Aud- Earth Aud+ Mute
White Black Red Blue Yellow
X X X X X
X X X
Red Yellow Blue
(used by control panel)
The unused yellow wire is perhaps used by the optional flashing cable. The separate power connector contains three colour coded wires (which are labelled so I wont spell them out here)