XM Antenna Failing

Hello, The Sierra may have the antenna under the headliner or behind the dashboard. Generally, if it is under the headliner, there will be a couple of hours of labor involved to remove and replace it, but there is no reason to go through that. The antenna will pick up signal through the metal chassis and dash pad, so I would simply replace it and secure it somewhere safe and somewhere it works. The old one can be left alone, and make sure you mark the old connector for what it is (bad old antenna).