It only needs to connect to the brown wire on the back of the headunit
Your comments make sense, what the the manufacture of the harness has confused me after enquiring about the connection, their comments as follow:
"The purple reverse trigger wire on the APVTY04 is to accept 12 volts when the car is in reverse.
It doesn't supply 12 volts reverse trigger .
So with connecting the head unit reverse trigger input AND this APVTY04 reverse trigger TO a 12 volt reverse trigger from the rear reverse lights is fine.
The purple wire to the APVTYO4 needs 12 volts on it when it is in reverse.
The APVTYO4 then converts the 12 volts to 6 volts that powers the factory camera."
Sorry, the link to the video here:
You can discover the wire from the 6-pin and avoid the bother of wiring the taillight to the head unit by watching a simple video on how to use a multimeter on YouTube.
This is what I am trying to achieve, need to find my meter and a good instruction video, however I fear damaging the equipment, does the car need to be turned on when testing?