Why is my MacBook Pro 2011 stuck on a white screen?

Give this a try to check things. Restart your system and press the T key to enter into Target Disk Mode. At that point the screen should show either a FireWire or Thunderbolt icon. Did it? If it does this is telling us the discrete GPU has failed and it can’t get past the startup POST process.

We can trick the system once you can get past POST. Here we can force the system to use only the integrated graphics engine within the CPU. But it’s not as good as the discrete GPU.

Sadly, this series suffered from a few different issues which are working against you. Frankly, I think the smarter solution is swapping out the logic board to a much better one! I can tell you I’ve done quite a few and my own 2011 is likewise running with a 2012 logic board. Review this guide MacBook Pro 15" Unibody Mid 2012 Logic Board Replacement basically it’s a clean swap out with one minor alteration to the display cable as Apple changed suppliers so yo need to use a common nail file to grind down the fiberglass tang ever so slightly equally from each side at the width is a bit narrower with the socket.