What is KingoRoot error code 0x15F6D5? I'm currently rooting a Samsung J1 Ace in Android 5.1.1 using KingoRoot in order to give Link2SD root access and move the apps, music, and other data files from its internal storage to a SD card. The internal hard drive has 8 GB and is almost full to the point where it can't update apps.

I've downloaded KingoRoot through the mobile browser as an APK file and enabled USB debugging. After a few minutes, it reports that the rooting process has failed and reports ERROR CODE: 0x15F6D5. I searched through forums and have found nothing on this error code.

What is it and how do I avoid it?
I don't think this phone model on this Android version can be rooted using any one-click method, especially those using  apps! Those apps/softwares seem to since from android 5 (Lollipop).

You can still try the desktop version which I doubt will succeed. 

Only Chainfire's rooting method can work. Works on every Samsung devices I had to root. The method consists of flashing a modified recovery by entering the device in Download mode. 

Also, I'll recommend you heading to XDA Developers  for extra details.

Follow the instructions form this site. Or this detailed rooting process from XDA Developers. Alternative solution from Tsar3000 site.

Find all rooting files for many Samsung devices from the developer's site.