Radio Removal

[2005GMCZ71]

O.k, first the vehicle in question::

2005 gmc sierra 1500 w/ 6 disc cd changer(in dash) and xm,and no visual "mast" style antenna

 

The question i have is:, I need to remove the H/U to check for a possible loose connection to the anntenna (virtually no f/m reception). Can i just pull the radio out far enough to check this connection, without actually disconnecting the power?

 

The problem is, i would assume this unit has a theft deterrent system, as there is a small, red, flashing light on the radio, when the ignition is off, and i bought this truck used, so i dont have a "code". So, i am hoping that G.M was thoughtfull enough to provide enough slack in the harness to allow partial removal, at least enough to get my hand behind the radio to see if the antenna is fully connected.

 

If not, i guess i'll just deal with it