need help on how to test the mmi system on a o6 audi A6 quatro 4.2 no power no comunication to the mmi system with scan tool engine computer is fine has comunication its just the mmi system checked alot of stuff obd wire in main wire loom to mmi computer green and lilac has 12.5 volts replaced the mmi control panel checked all the fuseas and grounds and the stering wheel buttons dont activate the shstem either