I thought I would ask seeing I didn't hear about the unit being tested or looking at your OnStar fuse? Does your onstar work if your press your onstar button? You can always press it and then say sorry it was an accident your adjusting your mirror!
Also did you test the Red/White wire back at the XM box also make sure that the Ground wire is good and connected? Again didn't hear anything about testing the unit.
I was happy to see that you pulled the headunit and made sure your Wires were connected, But just need a little more testing before Buying a Reprogram of another persons radio...
I would hate to see you connect it and pay to program and have it not be the issue after all...
James
To Test it, If you have a DMM or test light you could get to the wires without removing the unit. However to be safe, I would remove XM from car mount, lay unit down, Test it by back probing the connector. Also checking the ground at the unit and follow the ground to where it makes the connection to the Body and and make sure it is well grounded. Problem is that if you unplug it and test (Front probe) it could be that there is power enough to power test light but not enough to power the XM box.. Even though it don't take much power.
If you don't have DMM or Test light you might have someone at a Local Car Stereo shop do the testing for you... Some may do it with hopes you will come back and buy some upgrades. Some people may charge a Flat rate or Shop rate for testing.. Sadly there is in some cases if they not very kind. A minimum of an hour labor even if it takes 1 min.