Computers, Laptops & Tablets Apple Resetting the SMC (System Management Controller) on Your Mac When your Mac misbehaves, reset the SMC by Tom Nelson Writer Tom Nelson is an engineer, programmer, network manager, and computer network and systems designer who has written for Other World Computing,and others. our editorial process Facebook Twitter Tom Nelson Updated on May 18, 2020 Apple Macs iPad Tweet Share Email The System Management Controller (SMC) controls several Mac core functions. The SMC is hardware that is incorporated into the Mac's motherboard. Its purpose is to free the Mac's processor from having to take care of rudimentary hardware functions. With many core tasks performed by the SMC, resetting the SMC to its default state can fix problems. What the SMC Controls The list of functions controlled by the SMC is long and varies depending on the Mac model. Spencer Platt / Getty Images News The SMC performs the following functions: Responds to the press of the power button, including deciding whether the press is for power-off or sleep, or was a misstep by your cat.Detects and responds to the opening or closing of the lid of a portable Mac.Manages a portable's battery performance, including charging, calibration, and displaying the remaining battery time.Handles the thermal management of the Mac's interior by sensing the temperature inside the Mac and adjusting the fan speed to generate or reduce airflow.Uses the Sudden Motion Sensor to respond to the sudden motion of a Mac laptop and acts to prevent damage.Detects ambient lighting conditions and sets appropriate lighting levels for devices.Controls keyboard backlighting.Controls built-in display backlighting.Controls the status indicator lights.Selects external or internal video sources on iMacs with video input capabilities.Starts hard drive spin-downs and power-up sequences.Controls sleep mode functions.Controls trackpad functions for Mac models with trackpads. Signs You Need to Reset the SMC Resetting the SMC is not a cure-all, but it fixes many symptoms a Mac may suffer from, including: Erratic sleep mode performance, including not waking from or not entering sleep.Entering sleep unexpectedly, even while you are actively working.Mac laptops that don't respond to the lid opening or closing.Failure to respond to the power button being pressed.The power indicator doesn't display or displays incorrectly.Sluggish performance, even when the Activity Monitor shows little CPU usage.Target Display Mode doesn't work correctly.The battery isn't charging or takes excessive time to charge.USB ports aren't working.Wi-Fi hardware is reported as missing or not working.Bluetooth isn't working.Fans run too rapidly.The display backlight doesn't respond to ambient light-level changes.The status indicator lights don't work correctly or are stuck in a static state.Bouncing Dock icons keep bouncing without the associated app launching.Mac Pro (2013) port illumination fails to turn on or off. How to Reset Your Mac's SMC If you experience any of these symptoms with your Mac, resetting the SMC may be the fix you need. The method for resetting a Mac's SMC depends on the type of Mac you have. All SMC reset instructions require shutting down your Mac first. If your Mac fails to shut down, press and hold the power button until the Mac shuts down, which usually takes 10 seconds or so. Reset the SMC on Mac Notebooks With Nonremovable Batteries All MacBook Air models have nonremovable batteries. So do MacBook and MacBook Pro models that were introduced in mid-2009 until the present, except for the 13-inch mid-2009 MacBook. This method is not recommended for Macs with the Apple T2 security chip introduced in 2018. To reset the SMC: Shut down the Mac. On the built-in keyboard, simultaneously press and hold the left Shift, left Control, and left Option keys on the keyboard while you press the power button for 10 seconds. (If you have a MacBook Pro with Touch ID, the Touch ID button is also the power button.) This method does not work from an external keyboard. Release all the keys at the same time. Press the power button to start the Mac. Reset the SMC on Mac Notebooks With Removable Batteries Apple laptops with removable batteries include the 13-inch, mid-2009 MacBook, and all MacBooks and MacBook Pros introduced in early 2009 and before. Shut down the Mac. Remove the battery. Press and hold the power button for five seconds. Release the power button. Reinstall the battery. Turn on the Mac by pressing the power button. Reset the SMC on Mac Desktops With the T2 Chip If you have an iMac Pro or Mac Mini from 2018 or later or a Mac Pro from 2019 or later, it has an Apple T2 chip. You can confirm this in About This Mac in the Apple menu. To reset these desktop Macs: Shut down the Mac and unplug the power cord. Plug the power cord back in after 15 seconds. After five seconds, press the power button to turn on the Mac. Reset the SMC on Mac Notebooks With the T2 Chip The MacBook Air and MacBook Pro introduced in 2018 and later contain the Apple T2 chip. To reset the SMC on these notebooks: Shut down the Mac. Press the power button and hold it for 10 seconds. Release the button. Press the power button after a few seconds to turn on the Mac laptop. If your notebook computer problem continues: Shut down the Mac. Press and hold the right Shift key, the left Option key, and the left Control key for seven seconds. Continue to hold these keys while you press the power button for another seven seconds. Release all the keys at the same time. Press the power button to turn on the Mac. Reset the SMC on Other Mac Desktops The desktop computers that don't have the T2 chip, which is most of the ones made before 2018, include Mac Pro, iMac, and Mac mini. To reset the SMC on these devices: Shut down the Mac. Unplug the Mac's power cord. Wait 15 seconds. Reconnect the Mac's power cord. Wait five seconds. Start the Mac by pressing the power button. Alternative SMC Reset for Mac Pro (2012 and Earlier) If you have a 2012 or earlier Mac Pro that isn't responding to the normal SMC reset, force a manual SMC reset by using the SMC reset button located on the Mac Pro's motherboard. Shut down the Mac. Unplug the Mac's power cord. Open the Mac Pro's side access panel. Just below the Drive 4 sled and adjacent to the top PCI-e slot is a small button labeled SMC. Press and hold this button for 10 seconds. Close the Mac Pro's side door. Reconnect the Mac's power cord. Wait five seconds. Start the Mac by pressing the power button. Now that you have reset the SMC on your Mac, it should be back to operating as you expect. If the SMC reset didn't fix the problem, combine it with a PRAM reset. Although the PRAM works differently from the SMC, it stores a few bits of information that the SMC uses. If you still have problems, run the Apple Hardware Test to rule out a defective component on your Mac.