Ok so I hooked up the D3 to the Metra VT-GMOS-04 harness so that I could retain control of my chimes and Onstar. However, Onstar does not work! When I press the blue button the D3 shuts down, but I don't hear the familiar "Onstar Ready". When I press the blue button again to cancel, the D3 turns right back on. Any thoughts as to why this is?
I have done the D3 Mod (moving the mute wire up a slot to watch DVD while driving) does that have something to do with it?
Thanks! 
Do a search this is a problem that has a solution
I can confirm that adding a wire to the original mute location and connecting that to the GMOS mute wire will, in fact, mute the radio for onstar instead of turning it off/on.
yup it sure will.
nothing else but mute it.
i didnt have a spare wire so i just tapped the gmos wire into the og mute slot and it worked.
Good move...
Where can I find a wire pin for the wire harness? I want to add a wire to the plug to mute the stereo for Onstar calls.
Ok so I hooked up the D3 to the Metra VT-GMOS-04 harness so that I could retain control of my chimes and Onstar. However, Onstar does not work! When I press the blue button the D3 shuts down, but I don't hear the familiar "Onstar Ready". When I press the blue button again to cancel, the D3 turns right back on. Any thoughts as to why this is?
I have done the D3 Mod (moving the mute wire up a slot to watch DVD while driving) does that have something to do with it?
Thanks!
What did the manual tell you to do for the volume? (hint: brown loop)
Yeah cut the brown wire, and add a wire to where the mute wire you pulled out to make the ground mod to work. A little more than just cut the brown wire. 