MacBook Pro 2011 shows grey screen during boot My early 2011 MBP stopped booting up. It now shows only a grey screen after about 1/3 of the boot up process. 
I tried Verbose mode, where the last lines visible before the grey screen can be seen in the picture. 
Could it be a faulty GPU? It is a MBP from the era with defective AMD GPUs. 
So far I never had problems with it. 



I've read that I can disable the AMD gpu by moving away the AMD kexts. However single user mode gives me sandbox violations if I do this. 

The problem exists if I try to boot into Safe Mode as well.

I have run AHT extended and get a 4MEM/9/40… error. I guess this means the RAM is bad? Now trying only one module at a time. 

With only one module, I don't get errors. Tried three AHT passes. However I still can't boot. Not even recovery with Cmd+R. Next step: internet recovery. 

Internet recovery leads to the same grey screen and fans spinning. Next step: PRAM an SMC reset. 

SMC reset did not help either. I fear I am out of options. I guess I'll have to get the machine to a service place…
I had the same problem. Your GPU is dead. There was a recall awhile back for my late 2011 model. Maybe Apple will honor it and repair yours for free.