I have a Note 4 and use Android Auto. I've got the Pioneer AVIC-F77DAB unit in my car.
Works fine most of the time 9 out of 10 times it'll connect first time... Sometimes however it will give you the "Android Auto cannot connect right now. When it is safe to do so, please check your Android phone".
I can nomally get around that by disconnecting and reconnecting the cable. In rare ocassion I will have to restart my phone.
Other Issue I sometimes get is.. when Android Auto Starts up, and i have no volume control whatsoever Pioneer has somehow set to full blast... and I cannot lower it... again disconnecting and reconnecting it sorts it out. I have noticed that my dads S5 seems to have a not more problem connecting his phone to my Android Auto and my Note 4 does, but then again I think that is because of the way my dad starts the car.. as soon as he starts it he puts it in reverse gear (which switches to rear camera), while I normally wait for Pioneer to complete boot up before I do anything.
01-04-2016 03:35 AM