I have a similar problem. My iPhone 5 sometimes (three seperate times) won't connect to Carplay. I would turn on the headunit. The phone would turn on and request my passcode to access Carplay (my phone is always on lock mode) and the Carplay icon would appear on my phone but the head unit would say something along the lines of "Attempting to connect to Carplay" and the message display would turn off but never connect. Everything else works fine in the headunit except Carplay. I would turn on and off the heading several time to see if its a glitch but nothing worked.
I was ****** and tired that night so I went to bed with my mind to call pioneer in the morning. Before picking up the phone that morning, I decided to turn off and on my phone to see if I can boot my phone system (perhaps my phone was the one causing this issue) and sure enough I plugged my phone and Carplay was fully connect and functioning.
I never experience drops from Carplay mode of any kind in my few weeks with this headunit. I absolutely love the AppRadio 4. My only two gripes is that this connection with Carplay is becoming a serious issue and there is this very specific speck of dust that lies within the LCD screen of the headunit which really bugs. I'm slightly an OCD nut so this rubs me the wrong way. I tried returning this headunit for another, but it seem like the other unit had the same issue (in a different location of the screen.
Anyone here has this same problem, a speck of dust within the LCD screen of the headunit?