I have a 2004 X5 4.4i with Business cd DSP. I found the cd changer connectors in the back next to the amp. One is a 3 pin power cable and the other is a 6 pin cable. I've tried to connect a BMW changer that works fine in my other BMW 330Ci. The radio recognizes the changer and the cd's play but there is no sound. Any ideas why?