Ursprünglicher Beitrag von: arbaman ,
If you have performed all software tweaks found in system preferences/keyboard to no avail try resetting SMC: turn off the Mac, press shift+ctrl+alt+power..you'll see magsafe light going from amber to green and amber again. Boot the Mac and before the chime press alt+cmd+P+R and keep them pressed until the second chime to reset Pram. If no joy, try reseating the keyboard cable on the logic board. If none of these work, possibly you got a faulty topcase.