I bought a 2005 Tahoe LT with a new engine installed and it had problems with the CD player in that if you tried to put in a CD the whole radio stopped working. It had a good FM signal and now and then it got AM as well. I got another OEM radio, programed to my VIN and installed it. FM and all controls work (Steering wheel buttons, CD, Cassett, Radio) but there is nothing but static for the AM. While researching antenna possibilities I discovered the AM comes in when I turn the ignition off. There is one spot on the ignition that causes the AM to start working with a strong clear signal when the key is being turned to off. Once it starts working, I can turn the ignition off and take the key out and the signal will still work. If I turn the key to on, or start the truck, the AM signal disappears. There is no identifiable antennae in the right rear passenger window, the rear window or the right front fender well. There is a traditional mast antenna on the right front fender. Dealers and radio shops all want to look at the antenna they cannot locate. Prety sure, since it gets AM and FM it is not the antennas, but I am completely stumped on this.