Monkey Book Pro: PMU Reset

October 21, 2006

I experienced problems with my MacBook Pro not going to sleep properly after updating to Mac OS X 10.4.8. When closing the lid, the screen went black, but the Mac didn’t go to sleep itself and worked along happily.

What helped to solve this issue for me was a PMU Reset (PMU is the Power Management Unit/ according to Apple: “The Power Manager is an integrated circuit (computer chip) that is on the logic board of the MacBook or MacBook Pro. It controls backlighting, hard disk spin down, sleep and wake, somecharging aspects, trackpad control, and some input/output as it relatesto the computer sleeping.” ).

PMU reset for a MacBook/MacBook Pro:

  1. If the computer is on, turn it off.
  2. Disconnect the AC Adapter and remove the computer’s battery.
  3. Press and hold down the power button for 5 seconds and then release the button.
  4. Reconnect the battery and AC Adapter.
  5. Press the Power button to restart the computer.

By the way: Apple tells you to first try to restart your mac normally to solve the issue 😉

After some discussion with friends & apple service technicians, we recommend to hold down the power button for at least 10 seconds.

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