Matthewts

Do you have an interface to communicate with your factory system ? Most newer GM vehicles require that you have one. Some models are different for bose vs non-bose and onstar vs. no-onstar. Newer models will work for either. check out www.pac-audio.com

I, too, had this problem and just turned down the gain on the gmos-04 and it went away. I had to play with it to turn it up as much as possible without hearing the engine whine. It works great with the exception that now when I play my dvd sound through the input on the back of the unit the volume is very low. I have tried adjusting the vol for each source but it doesn't fix this one. Everything else, though, is fine.