The mute wire is for a phone kit… not reverse, the phone kit puts an earth out when you get a call, not sure why they put them on hu with built in bt nowadays

You could put it to a relay fed by reverse signal to mute it when reversing if you wanted… you need the relay as it is looking for an earth signal and the reverse will be positive switched on 99.9% of cars

As for the illumination, that needs to be wired to a side light feed not ignition or it will dim the illumination whenever you start the car, not when it’s dark and you put sidelights on

 

Hi thanks for your reply. I understand the mute is for a phone. Sorry I should’ve explained better…..how do I mute an external amp powering a sub when a call comes through or does the head unit automatically do this?