Audio Systems: cd changer/aux audio, harmon kardon, audio harness

Question
I am trying to hook up a Harmon/Kardon drive & play to my radio so I can use my ipod, I have hooked a aux audio harness to the cd changer port---no luck.  I've been told the factory/dealer has to activate the cd changer port, is this True?  Currently I am using my ipod through an fm modulator----sound quality is not all that good--I would like a direct link to the radio for supperior sound.  I have a 2005 silveraldo with in dash cd changer

Answer
direc ipod control from radio it will also display song information and artis

http://www.oemautosound.com/pc-265-151-usa-spec-pa11-gm-gmc-to-ipod-interface.as...

auxiliary interface new version
http://www.oemautosound.com/pc-304-151-pie-gm12-auxv2-gmc-auxiliary-adaptor-2002...