My MacBook Pro a1398 fails to boot completely. Gets to progress bar and goes to black screen

Check this technote which shows startup screens.

Startup Screens : About the screens you see when your Mac starts up

Also see:

Computer Won’t Start Up:

Try reseting NVRAM. How to Reset NVRAM on your Mac - Apple Support

Then try reseting SMC. Reset the System Management Controller (SMC) on your Mac - Apple Support

Then try a Safe Boot. Try Safe Mode if your Mac doesn't finish starting up

Also check out this help file. If your Mac won't turn on - Apple Support

Also check out this help file. Troubleshooting Startup and Login Items

Also check out this help file. Top 10 Troubleshooting Tips for Mac Startup Problems

Tackling Macs that always boot to Safe Mode. Tackling Macs that always boot to Safe Mode

Kim

I just had this problem and my hard drive had crashed. I hope you have better luck. I took it into Apple and was told it might be a cable problem, an easier fix, but alas, this was not the case. I knew there were some home solutions but since I had some backup issues, I took it to the Genius bar. Good luck.

This MIGHT be your problem:

https://www.apple.com/support/macbookpro-videoissues/

Make an appointment at an Apple store genius bar and have it tested.

Ciao.