am / fm not working too well

[teakman]

Just got a 2004 Tahoe LT and the radio is acting weird. AM/FM will not get in more than 2 stations. I plugged a new antenna into the factory radio and it worked great ?? So its the antenna obviously ... Question is, I've traced the antenna thru the dash, up the rail by the window, thru the headliner and all looks well. It seems to plug into a the little stubby antenna on top and I believe it shares this with Onstar. I even replaced the little stubby with a new antenna mast but nothing ?

Is there a relay somewhere that could be out ?

Thanks