I have a 2001 yukon xl with onstar that is not used. I bought a new aftermarket stereo and installed with provided harness adapter. Power comes on and everything seems to work on the HU, but there is no sound. I searched around the web for anyone that might have the same problem but came up with only a few similar questions. the understanding i have is that the factory amplifier will conflict with the preamp built into the aftermarket stereo. but how do you bypass the preamp? The remote antenne is hooked up to the remote wire on the harness, but nothin'. Now there is the main harness input on the factory radio, and there is another 10 or so pin harness that also attatches to the back of the factory radio. There is nowhere for this other 10 pin connector to go on the aftermarket unit or harness adaptor. Is this related ? Someone PLEASE help!!!