Reset the SMC
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.
If you have a 2016 MacBook Pro with Touch ID, the Touch ID button is also the power button.
4. Release all keys.
5. Reconnect the power adapter.
6. Press the power button again to turn on your Mac.
How to reset NVRAM on your Mac
If you experience issues related to settings stored in NVRAM, resetting NVRAM can help.
NVRAM (nonvolatile random-access memory) is a small amount of memory that your Mac uses to store certain settings and access them quickly. Settings that can be stored in NVRAM include sound volume, display resolution, startup-disk selection, time zone, and recent kernel panic information. The settings stored in NVRAM depend on your Mac and the devices you’re using with your Mac.
If you experience issues related to these settings or others, resetting NVRAM can help. For example, if your Mac starts up from a disk other than the one selected in Startup Disk preferences, or a question mark icon briefly appears before your Mac starts up, you might need to reset NVRAM.
Older Mac computers store similar information in PRAM (Parameter RAM) instead of NVRAM. The steps for resetting PRAM are the same as the steps for resetting NVRAM.
How to reset NVRAM
Shut down your Mac, then turn it on and immediately hold down these four keys together: Option, Command, P, and R. Keep holding the keys for about 20 seconds, during which your Mac might appear to restart. (If you have a Mac that plays a startup sound when you turn it on, you can release the keys after the second startup sound.)
When your Mac finishes starting up, you might want to open System Preferences and adjust settings that have been reset, such as sound volume, display resolution, startup disk selection, or time zone.