How to test power button with multimeter

First you’ll need to take the uppercase off MacBook Pro 15" Core 2 Duo Model A1211 Upper Case Replacement. Follow the steps upto Step10. Then jump down to Step30 Here you can see the back side of the power button (green piece in top left with the two Red wires. Using your meter you should be able to test the button.

To be honest I haven’t see to many failed buttons. If your system won’t power up then leave the keyboard connected and carefully short out the red wires to by passing the button it should start up if not you’ll need to look deeper.