Aftermarket with OEM Mic

Hey Everyone,

I've been browsing through and trying to see if anyone has been successful in using the built in mic with an aftermarket head unit.

My girlfriend wants to update the head unit in her 2013 Prius C two. I can't blame her - that unit is terrible to use. It would be nice to get something Android Auto or at least full touch screen.

However, the one thing that is amazing is call quality and as far as she is concerned using the built in mic is a must because it picks up so well. We put an after-market Kenwood in my Scion xB and the mic on it is awful and won't mount right anywhere. The Prius C - perfect. She doesn't want something wired around the car, or sticking out, or that doesn't pick up, so basically the built in mic or nothing.

I'll be doing the installation myself, and while I have done a couple of head units, I'm not great at these kinds of things. So my question is, does anyone know how to get the mic to work / has anyone actually done it?

I've browsed around on Reddit and here and haven't found much promising. For example, Stock Bluetooth Mic Integrated Into After Market Stereo | PriusChat discuss it and shows that there should be pinning in the harness for it, but no one there seems to have completed it. The few cases that have said they've done it are not well documented.

Any help is appreciated.