My 2015 Lariat came with sync 2. After a couple of years I installed a Phoenix radio. It started getting glitchy so I decided to go back to the factory set up. It would never come on so I figured it was just bad. Decided to upgrade to sync 3, got it all installed, nothing. No functionality at all. Screen does not even illuminate. I have disconnected the batter to reset it, unplugged and plugged it back up several times just to be sure of good connection. No fuses blown, Nothing. Anyone have any kind of idea of why this is? Should I chalk it up to a bad unit? I just find it awfully coincidental for 2 units to be bad. Any fees back is appreciated.

 

What did you change? the APIM and the screen or just the APIM? For Sync 3 you need to swap the entire assembly. If you only changed the APIM it's possible the screen isn't powering up but the Sync 3 APIM is booting up.
Connect to your laptop to the OBD module and scan to see which modules are present, if the APIM is good it will show up in list. Fuses don't tell you everything, put a multi meter to good use and confirm your power. Also without the FCIM and ACM connected it's possible your Sync 3 APIM may not be receiving the boot up signal from the gateway so check that everything is plugged in correct.

This explains the entire process: http://www.2gfusions.net/showthread.php?tid=3881

If your APIM display output is dead, sometimes a firmware update will bring it back to life which is a bit of a hack for restoring 'bad' eBay APIM's but should be an absolute last ditch approach.