I got a D1 that started making a high pitch noise, similar to engine noise. I have pulled everything out and redone everything from scratch. Moved the grounds. Redid all the speaker connections and everything. I was about to give up when I noticed as I was sliding the unit back into place that if the Front Output of the AV cables were bent in such a way, everything was fine. Is it possible for the AV harness to go bad? Or could there be something else?

It could be an issue of grounding your RCA cables. And when you pushed the unit back in, they touched some metal part and grounded out, eliminating the ground loop, and in turn eliminating the noise.

Either that, or the end(s) of your RCA cables are going bad and causing a loose connection. Happened to me once. The connector at the end of one of my RCA cables was coming apart and it caused a hellish whining noise. I replaced the cable and it sounded fine.

Them I am assuming that changing out the AV harness should be the cure. The RCA cables leading from the amp are brand new. Like I said it's grounding the AV harness cables that help.

I had the same problem with mine. I found that if i grounged the RCA shielding to the chassie of the D1 it stopped the noise.

Yeah. Don't go buying a new harness/adapter/whatever. Just ground the RCA cables first. It should take care of the noise.