98 Tahoe amp/sub help

Some gm vehicles have a antenna amplifier that also needs to be given a 12 volt signal, is yours one of them, I cannot be sure. Did you have am reception before powering up the amp? Do you have another wire in the factory harness that when the factory radio is in reads +12v when the tuner is used? Most factory radios have an amazing tuner in them, most aftermarket do not. FM radio is pretty much not bad for any aftermarket but AM leaves a lot to be desired. The last time I ran into this kind of problem it was in a 03 Buick Regal and it had the hidden antenna module, once this module was powered up, presto, AM reception again.Top Secret, I can tell you but then my wife will kill me.

The am radio reception was fine prior to powering up the amp. Nothing was done to the wiring harness that had not already been in place for many days. FM reception is fine.

you gotta power the blue wire coming off the aftermarket GM harness.  it turns on a factory amp that runs your back speakers..ive seen this before.  so the remote wire to ur amp, the blue wire on the GM harness(even though it may say power antenna) and the blue/white wire remote output on ur headunit all need to be connected together

the wiring is as follows. Remote from amp wired to blue with white stripe wire. Rear speaker wire (back door only, not rear deck) also blue, is wired to same blue/white wire. The rear door wire was moved to the blue/white wire yesterday after the rear door speakers wouldn't work on cd, and the am radio reception was non existent. That fixed the problem. Until today, when the am reception is gone again. all else is working fine. The only wire that is currently not being used is another blue one that the rear door speakers were connected to as of yesterday. They worked fine until the amp was powered up. That blue one is now capped.

Update: The problem ended up being a bad section of coax wire. I had the section repaired once previously and with the multiple removal/re-installations of the head unit the repair failed. All is well now. thanks for everyone's help.