Hello all, my 1st post with my latest Hummer H2. In 2004 in Chicago I almost bought one new but it didn't work in the garage. Now in Texas, this is my 2nd.
Everything "seems" factory about the radio and entertainment system.
However trying to listen to XM yields "Antenna" on the radio display. Not no signal, but a message that seems to indicate a problem or lack of antenna.
What I have found inside the dash is an interesting mix of boxes and wires (beside the aftermarket prestige alarm).
After removing the head unit, I did find an antenna cable connected. I honestly didn't trace that wire as it seems to go into a loom. However behind the glove box I found a Sirius box with and antenna also connected. That cable is way long and looped up and I assume aftermarket.
I do see what appears to be the factory XM coaxial cable but that is not connected. It seems the factory plug doesn't connect to the Sirius box mentioned above. It can be seen as the Fakra Curry K connector, vs. the other 90 degree connector.
The output of the Sirius box looks like S-video (I know I'm old school) can goes to a box called a Soundgate CD Changer interface. From there it seems to be spliced into the smaller factory head unit connector.
I'm not sure why anyone would do this. As mentioned this truck has the factory DVD and screens but from what I can see that entertainment system has nothing to do with the dash mounted radio or XM.
Any advise? Do I need any of this for XM? I thought the factory XM was built into the head unit but maybe not? Is the coax cable into the head unit for Nav? Or is there some OnStar complication as well?
I appreciate your input in advance. Thanks!

The factory (above) and non factory (below)

Is this a stock Sirius device?

No clue why this is here.