Guys, you need the actual hardware component for this to work. Its a GM NAV/DVD UNLOCK interface that goes between the radio and the oem harness. Than with this installed the 4 Mute button depressions works. NO CODE or SECRET way will allow NAV/DVD to play unless you get the interface. Links and pasted content from website below.
TIRED OF LOOKING AT THIS?
GET A GEN 5 LOCKPICK FROM COASTALETECH!!
Instructions and Operating Manual:
http://www.coastaletech.com/media/GEN5.pdf
HUMMER INTERFACE
http://www.coastaletech.com/HUMMER_APPLICATIONS.htm
ESCALADE INTERFACE
http://www.coastaletech.com/GMLOCKPICK.htm