2003 GMC Sierra 1500 Pickup Owner's Manual - Page 260

y Message XMTMRadio Messages (cont'd) I Not Found XM Locked message after having your vehicle serviced, check with the servicing facility. Radio ID Radio ID label (channel 0) Radio ID not known (should only be if hardware failure) Hardware failure If you tune to channel 0, you will see this message alternating with your XM Radio 8 digit radio ID label. This label is needed to activate vour service. Unknown If you receive this message when you tune to channel 0, you may have a receiver fault. Consult with your dealer. If this message does not clear within a short period of time, 3-105