Chosen Solution

My Problem is as follows:

  1. the MacBook swtiches of w/o warning during boot
  2. any of the “standard” procedures (SMC-reset, etc) don’t help
  3. Apple Hardware test runs (fans at full speed) and shows not errors
  4. booting while pressing any (?) key (I tried with shift, D so far) boots the system up with fans running at full speed, key always pressed
  5. fan control programs like smcFan Control do not see any fans or temperatures
  6. as soon as I realese the pressed key the system switches of almost immediately Any ideas?

It could be quite a few different causes. can you please give us some background on what proceeded. Did you get your system wet or spill something into it? Update (01/04/2017) Here’s the IFIXIT guide to get to the keyboard: MacBook Pro 13" Unibody Late 2011 Upper Case Replacement. It’s a bit of work and you still need to disassemble the keyboard from the uppercase.