I just purchased a new XM because my old one stopped working. When I was talking to XM service dept. trying to switch my service to new radio, the woman told me that they were forced to lower their signal strength (via the fm station) on their newer radios and they would not work on all cars. She said the new unit may not work as well (or at all) as my old one and I may need to get it hardwired to the car. When I installed it, it did receive spotty reception whereas my signal used to be excellent. Not sure if this is your problem but you may need to bring in your car and have it hardwired. Most places that sell the XM, such as Best Buy, also install or can at least tell you someone who can.
