Asking for a friend here, he has an Audi a4 b7 05 plate with ISO connections, non Bose half amplified rears.
He purchased the CTSDA003 cable from me as well as my stereo.
I have faded the sound to the rear speakers. However there is one extra cable coming from the car.
Do I need to hook this up? It looks like the dual fuse part? It's yellow. I forgot to take a picture before he left....