I just bought an AVIC-D3 and bypassed the lock out system as described on this forum (Thank you very much) I'm just curious if any body knows what circuit we actually grounded when we move the mute wire? Just interested in knowing. I hate to do things blindly but I did it anyway and it works fine.

The circuit doesn't really have a name, per se, as it's never used for anything, it's never referred to in any of Pioneer's manuals or anything. Other than the bypass, of course. If you're asking whether it's compromising another function by enabling another, no. Quit worrying about it so much and enjoy the end results.

Was not worried about it. Just my curious nature.

I read somewhere that it was for service...

Yeah... by-pass service!