I recently received an interesting tip and the picture above from one of our readers, Ian. He recently purchased a Pioneer AppRadio 4 (SPH-DA120) and discovered it's running firmware version 1.08. What makes this interesting is that Pioneer's website only has version 1.07 as the latest firmware which was available back in October, 2014.
Version 1.08 is nowhere to be found for download on any of Pioneer's websites (US or Global). Whether there's anything different in version 1.08 from the previous 1.07 is not clearly known, but a forum thread in Apple Support Communities may offer some clues.
If you read this thread on Apple's website, you will notice users complaining about dropped connections when using CarPlay on an AppRadio 4. One user even says CarPlay doesn't even launch on his/her unit.
But then, another user suggests no issues running CarPlay on his AppRadio 4 from his iPhone 5 running iOS 8.1.3. The only difference is, his AppRadio 4 has version 1.08 installed on it (probably a new purchase too). That post is from March 3, 2015.
Here is a screenshot of Pioneer's website showing version 1.07 as the only available download for the AppRadio 4...
I have emailed Pioneer Support regarding this and am awaiting a reply. Stay tuned for the latest.