I have a D3 bypassed that is making a high pitched noise....does it need to be regrounded or is something else wrong?

GROUND, GROUND, GROUND!

I just went through the same thing on my initial install in an '02 Toyota Sequoia.

There's lots of threads on this, but here's what I did to resolve it...

http://avic411.com/forum/viewtopic.php?t=7966

Good luck!

jan j