I run an AppRadio 4 (DA120) with an iPhone 6+ w/IOS 8.3 and everything works perfectly in both CarPlay mode and AppRadio mode.
The latest firmware is available on the Pioneer download page as 1.07 (new units indicate 1.08 but they are the same image and the number was changed by Pioneer to indicate the head unit production date). Pioneer claims they will not be providing a 1.08 for download for the DA-120.
For a variety of problems check the Pioneer output and smartphone settings as well as look at the iPhone settings for display, the Pioneer head should show (under General below "Siri"). Carplay requires iPhone 5 or later.
Some common AppRadio 4 issues:
- Did you connect the parking brake lead? It is critical this is wired right - I don't trust the gizmos that claim they bypass the function.
- For AppRadio mode with video display you need to have an HDMI cable and USB to Lightning going to an Apple Digital A/V adapter.
- You also need to change the Pioneer settings to HDMI out instead of USB or you will get a USB error.
- For CarPlay you cannot use the Apple Digital A/V adapter and you must use USB1 port to Lightning plug on the iPhone
- For CarPlay the Pioneer settings must be "USB" and smartphone "CarPlay"
- Check the firmware on the Pioneer head unit, it should be 1.07 or 1.08.