2003 Cadillac CTS Owner's Manual - Page 254

Diversity Antenna System Your AM-FM antenna is integrated with your rear window defogger, located in the rear window. Be sure that the inside surface of the rear window is not scratched and that the lines on the glass are not damaged. If the inside surface is damaged, it could interfere with radio reception. Do not apply aftermarket glass tinting. The metallic film in some tinting materials will interfere with or distort the incoming radio reception. NOTICE: Do not try to clear frost or other material from the inside of the front windshield or rear window with a razor blade or anything else that is sharp. This may damage the grid lines and affect your radio's ability to pick up stations clearly. The repairs wouldn't be covered by your warranty. If, when you turn on your rear window defogger, you hear static on your radio station, it could mean that a defogger grid line has been damaged. If this is true, the grid line must be repaired. If you choose to add an aftermarket cellular telephone to your vehicle, and the antenna needs to be attached to the glass, be sure that you do not damage the grid lines for the AM-FM antennas or place the cellular telephone antenna over the grid lines. 3-33