From what Joel_Bug said, he is doing it correctly.
A little more info on the model year and head unit type would be helpful.
I am assuming he has a silver button Premium 7 with internal 6 disc CD changer.
There is a hack on that unit that some people have done
where they hook up aux through the sat tuner inputs.
That trick requires the external sat tuner still be connected to work,
they just steal the audio inputs normally used by sat radio,
and those inputs will not work without the sat radio tuner handshake through the CAN-BUS.
Joel_Bug, does your sat radio work?
If not, try connecting your device and selecting satellite radio.