Can I resuscitate this issue? I installed the same ipod adapter oem with the 4 wires and same color code wiring. I have an 03 525i w/DSP and there weren't 4 wires on the adapter - leaving out the white/purple wire.

I thought I hooked the other 3 correctly but now looking at the number above I think they are wrong.

Nonetheless, I had ipod controls just no volume. The volume is working on CD as well as radio...

Any thoughts? What are the wires EXACTLY for? I know brown is ground...