Peugeot 307 Blaupankt CD Changer IDC-A09
Hi, I know this is an old post, but I'll reply, so that other readers may get the benefit of my answer.
2004 was the year that Peugeot/Citroen changed from VAN bus to CAN bus wiring on their stereo's. If your car is before or early 2004 you will need the IDC-A09 blaupunkt in dash changer, which should just plug in and work straight away.
However, If your car is later 2004 onwards you will need the IDC-A04 Blaupunkt changer which will plug in and power up, but will not work properly untill you go to a peugeot dealer and they hook up some diagnostic software to tell the car a changer has been added. Both the IDC-A04 and A09 changers look identical.
I would say that you got the wrong changer, as the IDC-A09 changers in pre/early 2004 should just plug in and work.
Remember: Pre 2004 cars need IDC-A09 (plug and play) and Post 2004 cars need IDC-A04 changer (get pug dealer to reprogram cars computer)...its a costly mistake if you bought the wrong one!