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Reset the System Management Controller (SMC) on your Mac

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Posted: 27 Feb, 2017
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Updated: 02 Mar, 2017
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Reset the System Management Controller (SMC) on your Mac

Learn when and how to reset the System Management Controller (SMC) on an Intel-based Mac. 

Before resetting the SMC

Reset the SMC only after you've tried all other standard troubleshooting. Try each of the following steps in this order before you reset the SMC. Test the issue after completing each troubleshooting step to see if the issue still occurs.

  1. Press Command-Option-Escape to force quit any application that's not responding.
  2. Put your Mac to sleep by choosing Sleep from the Apple menu. Wake the computer after it's gone to sleep.
  3. Restart your Mac by choosing Restart from the Apple menu.
  4. Shut down your Mac by choosing Shut Down from the Apple menu.
  5. If your Mac isn't responding, force the Mac to shut down by pressing and holding the power button for 10 seconds. You'll lose any unsaved work in any open applications.

If you're using a Mac notebook computer that's having issues related to power or the battery:

  1. Unplug the power adapter from your Mac and the electrical outlet for several seconds, then plug it back in.
  2. Shut down your Mac. 
  3. Remove and re-insert the battery, if it's removable.
  4. Restart your Mac.

If the issue still isn't resolved, you might need to reset the SMC. See the indicators and steps below. 

Indicators that the SMC might need to be reset

After you perform normal troubleshooting, these symptoms might mean that an SMC reset could be necessary:

  • The computer fans run at high speed, though the computer isn't experiencing heavy usage and is properly ventilated.
  • The keyboard backlight behaves incorrectly.
  • The status indicator light (SIL) behaves incorrectly.
  • Battery indicator lights, if present, behave incorrectly on Mac notebooks that have a non-removable battery.
  • The display backlight doesn't respond correctly to ambient light changes.
  • The computer doesn't respond to the power button when pressed.
  • A Mac notebook computer doesn't respond properly when you close or open the lid.
  • The computer sleeps or shuts down unexpectedly.
  • The battery doesn't charge properly.
  • The MagSafe power adapter LED doesn't indicate the correct activity.
  • The computer is performing unusually slowly, though it isn't experiencing abnormally high CPU utilization.
  • Application icons bounce in the Dock for an extended amount of time when opened.
  • Applications don't function correctly, or they stop responding after being opened.
  • A computer that supports target display mode doesn't switch into or out of target display mode as expected, or it switches into or out of target display mode at unexpected times.
  • The illumination around the I/O ports on a Mac Pro (Late 2013) doesn't activate when you move the computer.

Reset the SMC on Mac notebook computers

First, determine whether the battery is removable. Mac notebook computers that have a nonremovable battery include MacBook Pro (Early 2009) and later, all models of MacBook Air, MacBook (Late 2009), and MacBook (Retina, 12-inch, Early 2015) and later. Learn more about Mac notebook batteries.

If the battery is nonremovable:

  1. Shut down your Mac.
  2. Unplug the MagSafe or USB-C power adapter from your computer.
  3. Using the built-in keyboard, press Shift-Control-Option on the left side of the keyboard, then press the power button at the same time. Hold these keys and the power button for 10 seconds.
  4. Release all keys.
  5. Reconnect the power adapter.
  6. Press the power button again to turn on your Mac.

If the battery is removable:

  1. Shut down your Mac.
  2. Disconnect the MagSafe power adapter from your computer.
  3. Remove the battery. (Learn about removing the battery in MacBook and MacBook Pro computers.)
  4. Press and hold the power button for 5 seconds.
  5. Reconnect the battery and MagSafe power adapter.
  6. Press the power button to turn on your Mac.

The LED on MagSafe power adapters might change colors or temporarily turn off when you reset the SMC.

Reset the SMC on Mac desktop computers

Follow these steps for iMac, Mac mini, Mac Pro, and Xserve.

  1. Shut down your Mac.
  2. Unplug the power cord.
  3. Wait 15 seconds.
  4. Plug the power cord back in.
  5. Wait five seconds, then press the power button to turn on your Mac.

For Intel-based Xserve computers that aren't responding, you can shut down locally or by using remote commands. You can also shut down by pressing and holding the power button for five seconds.

Learn more

Resetting the SMC doesn't reset or otherwise change the contents of NVRAM or PRAM on Intel-based Mac models.

The SMC is responsible for these and other low-level functions on Intel-based Mac computers:

  • Responding to presses of the power button
  • Responding to the display lid opening and closing on Mac notebooks
  • Battery management
  • Thermal management
  • SMS (Sudden Motion Sensor)
  • Ambient light sensing
  • Keyboard backlighting
  • Status indicator light (SIL) management
  • Battery status indicator lights
  • Selecting an external (instead of internal) video source for some iMac displays

Published Date: Jan 12, 2017

Cr: https://support.apple.com/

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