so i am installing the f90bt. i have the Metra 70-1787 wiring harness for my 2002 Audi A4 w/bose system.

I cant get the unit to power on. I have noticed something. the ACC and Illumination wires on the metra harness plug in empty slots on the cars harness. what is that about? i have pictures.

the front of the stock power harness

back of metra harness

its not making sense to me, why the acc red and illumination orange wires plug into nothing on the stock harness.

On the stock power harness which is (wire color wise) the power wire? the illumination wire?

excuse the crappy bb curve pics

another question, must ACC and Constant power be connected in order for unit to work? can i just have acc connected?

Both must have power. You can check but I don't think the 2002 Audi has a ACC wire. Audi, VW and a few other have a data wire that tells the factory radio to cut on and off. Usually you can get ACC or IGN from the fuse box and run a new wire over to the deck.