I'm also desperately seeking information on this.
Want to keep the original head unit but work out how to make myself an auxilary input.
Have anyone tried to connect a mp3-player to the cd-changer interface in the trunk of a Peugeot 406 (2003)? I think the radio is a Clarion/VDO RC280 but I havn't been able to find any information about the cd-changer interface anywhere (pinout or communication protocol).
there is possibly some sort of aux in enabling device. I would have a look at some car audio sites - I remember a pretty good UK one getting mentioned on here that sells that kind of thing for OEMs. Have a dig around and see what you can find.