How do I reset the System Management Controller (SMC) or Power Manager (PMU)?

The power manager is used to control fans, heat sensors, and startup. On Intel-based Macs the power manger is called the System Management Controller (SMC). On PowerPC-based Macs (G4 and G5) this part is known as the Power Management Unit (abbreviated PMU). You should not arbitrarily reset the power manager. However, you may need to reset your SMC or PMU if you encounter one of the following symptoms.

1. Computer does not turn on when power button is pressed.
2. Portable computer does not sleep or wake correctly when lid is opened or closed.
3. Fans run on high when the system is not warm.
4. Battery is not charging when it should be.
5. Yellow and green indicator light on portable Mac’s power adapter behaves incorrectly.
6. Display or keyboard backlight adjustment does not work properly. By default your screen brightness should change depending on the brightness of the light around you (unless you’ve turned that feature off in Display preferences)
7. System is running unusually slow even when not under heavy use.

Before resetting the SMC, try these troubleshooting steps first.

1. If any of your applications are not responding (frozen), press Command-Option-Escape to force quit them.
2. Put your Mac to sleep by going to the Apple () menu in the upper-left corner and choosing “Sleep”. Then wake up the Mac after it has gone to sleep by pressing the space bar.
3. Shut down your Mac by choosing “Shut Down” from the Apple () menu.

If you are experiencing issues with your MagSafe power adapter or battery, try this:

1. Unplug the power adapter from the Mac and then the wall power outlet for a moment.
2. Shutdown the Mac normally. If you can remove your computer’s battery, do so and then re-insert it. Restart your Mac.

Here’s how to reset the power manager on different Macs (search www.apple.com/support for “reset PMU” or “reset SMC” for the latest info with pictures):

Intel iMac, Mac mini, and Mac Pro

If it’s on, turn it off. Disconnect all peripherals and the power cord. Keep it unplugged for at least 15 seconds. Then plug in and restart.

Any Portable Intel Mac with a removable battery and PowerBook G4 (15-inch 1.67/1.5 GHz, 17-inch 1.67 GHz)

If it’s on, turn it off. Disconnect the AC adapter and remove the battery. Press and hold the power button for five seconds, and then release. Reconnect the battery and AC adapter, and restart.

Any Portable Intel Mac with a battery you can NOT remove

If it’s on, turn it off. Connect the power adapter to a working power source. Press the (left) Shift-Control-Option keys along with the power button once. (You must use the keys on the left side of the keyboard.) Wait 5 seconds and press the power button to start the Mac.

PowerBook G4 (12-inch & 12-inch DVI, 1.33/1.5 GHz, 15-inch FireWire 800/1.33 GHz, and 17-inch 1.33/1.5 GHz)

If it’s on, turn it off. Simultaneously press then release the keys Shift-Control-Option-power button. Do not press the fn (function) key using this combination. Wait at least five seconds, and press the power button to restart.

PowerBook G4 (15-inch DVI, 1 GHz, and 867 MHz)

If it’s on, turn it off. Flip down the two keyboard latches located between the Esc and F1 keys, and the F11 and F12 keys. Lift the keyboard. Press and release the reset button located on the upper right side of the logic board near the power button. Wait at least five seconds, flip the keyboard back into place, and press the power button to restart the computer.

G4 PowerBook (FireWire and Gigabit Ethernet) and iBook (Dual USB and later)

If it’s on, turn it off. Press the reset button next to the video port on the back or side of the computer. Wait at least five seconds and then press the power button to restart.

Published March 24, 2009 12:00 PM
Last modified on November 25, 2011 11:27 AM