When I connect my HTC M9 to AVH4100NEX To use Android Auto all the functions work fine, except when I start GPS navigation "google Maps" , it seems when the screen goes black on my phone "it stays on a few seconds then "turns off" it takes the GPS signal with it ...so if I keep powering it on the blue arrow starts moving and I get the voice directions also but once it goes black the HU unit says "searching for GPS signal " I'm trying to figure out how to keep the screen on or what internal setting I'm missing on my phone or HU..sorry for so many quotations marks,this is my first post Eva!!!

Does it go fully black, or does it gray out????

I found that the GPS on my Moto G Play (4th gen) sucks, it uses the snapdragon410, so your processor on your phone might vary, but the GPS in this phone can't hold a GPS lock while driving.  I ended up buying an external GARMIN GLO gps reciever which acquires satelites very quickly and maintains an awesome lock at speed and in cities. 

When the gps goes out on my moto G(with built in GPS), the screen grays out and says "searching for gps".