Does yours come radio with SYNC/USB support? If so, look behind the radio for the Accessory Protocol Interface Module (APIM). There is a +5v violet/grey wire coming out of pin 8. This is directed to the USB port in the glove box or center console, and you can tap into that without having to use an auxiliary 12v-5v converter. It is not a true ACC wire, in that it will also be powered on when the radio is on without a key, but will also shutdown automatically, with the radio, after a predetermined time. I would use that wire if possible, rather than adding an additional transformer.