I want to wire an external device (in this case an XM Roady receiver) into
my 2004 Honda Accord audio unit.  This will be much better than using the
FM transmitter and will allow me to also plug in MP3 players, etc.  I have
the detailed Accord shop manual with schematics.  I will be hot wiring and
splicing from the Roady's headphone jack into the back of the dash unit.

The unit has a CD/AUX button (separate from the AM/FM button) but it seems
to need some type of signal to allow me to actually get to the AUX part of
the system.  Maybe a ground from the Roady?  Right now, all I get is the CD
side no matter how many times I hit the button.  Is this correct?  If so,
the manual shows locations for a recvr ground and a recvr bus ground?  
What is the difference??

Thanks for helping!!