Originally Posted by gstrekkie
Hi I have run into this a few years ago with my trailblazer. If you have the stereo controls in the back seat area that may be your culprit. I have an lt with the bose system I found some links here that helped. In a nutshell use some dialectric grease on the connector located inside the center console that connects the rear entertainment controls. changing the head unit might not have an effect especially if you are still using the same wiring harness and the stock amplifier. I havent heard the noise for a few years since I did that. Good Luck hope this helped!
I did this and for good measure, dielectric greased up the main purple connector underneath in the middle of the console while I had it all torn apart looking for possible reasons for this issue. Also wrapped some electrical tape over the metal bracket down there where it is fastened. Seems some fixed it by just unplugging and replugging in the harnesses.
I realize this does not help you but try some dielectric grease on your head unit harnesses.