Resetting the system management controller (SMC) can resolve certain issues related to power, battery, fans, and other features.
Notebook computers with a nonremovable battery
This applies to MacBook Pro models introduced in mid-2009 through 2017, MacBook Air models introduced in 2017 or earlier, and all MacBook models except the MacBook (13-inch, Mid 2009).
- Shut down your Mac. Plug in your computer.
-
On your built-in keyboard, press and hold all of these keys:
- Shift
on the left side of your keyboard
- Control
on the left side of your keyboard
- Option (Alt)
on the left side of your keyboard
- While holding all three keys, press and hold the power button as well.
- Keep holding all four keys for 10 seconds.
- Release all keys, then press the power button to turn on your Mac. You should see the power light on the charger briefly flash off and then back on again.
About the SMC
The system management controller is responsible for managing behaviors related to these features:
- Power, including the power button and power to the USB ports
- Battery and charging
- Fans and other thermal-management features
- Indicators or sensors such as status indicator lights (sleep status, battery charging status, and others), the sudden motion sensor, the ambient light sensor, and keyboard backlighting
- Behavior when opening and closing the lid of a notebook computer
Resetting the SMC doesn't affect the contents of NVRAM or PRAM.