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 December 07, 2019 Apple Macs iPad Tweet Share Email The System Management Controller (SMC) controls a number of 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, it is no wonder that resetting the SMC to its default state can fix problems. What the SMC Controls Spencer Platt / Getty Images News The SMC performs the following functions, which vary by Mac model: Responds to the press of the power button, including deciding whether the press is for a power-off, sleep, or caused an accidental misstep by your catDetects and responds to the opening or closing of the lid of a portable MacManages a portable's battery performance, including charging, calibration, and displaying remaining battery timeHandles the thermal management of the Mac's interior by sensing the temperature at various places inside the Mac and then adjusting fan speed to create or reduce airflowUses the Sudden Motion Sensor to respond to the sudden motion of a Mac laptop and acts to prevent damageDetects ambient lighting conditions and sets appropriate lighting levels for devicesControls keyboard backlightingControls built-in display backlightingControls the status indicator lights that are present on or in the MacSelects external or internal video sources on iMacs with video input capabilitiesStarts hard drive spin-downs and power-up sequencesControls sleep mode functionsControls 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 sleepEntering sleep unexpectedly, even while you are actively working on itMac laptops not responding to lid opening or closingFailure to respond to the power button being pressedPower indicator not displaying or displaying incorrectlySluggish performance, even when the Activity Monitor shows little CPU usageTarget Display Mode not working correctlyBattery not charging or taking excessive time to chargeUSB ports not workingWi-Fi hardware reported as missing or not workingBluetooth not workingFans running too rapidlyDisplay backlight not responding to ambient light-level changesStatus indicator lights not working correctly or stuck in a static stateBouncing Dock icons that keep bouncing without the associated app launchingMac Pro (2013) port illumination fails to turn on or off How to Reset Your Mac's SMC The method for resetting your 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 Mac Notebooks With User-Removable Batteries Shut down the Mac.Remove the battery.Press and hold the power button for at least five seconds.Release the power button.Reinstall the battery.Turn on the Mac. Reset Mac Notebooks Without User-Removable Batteries Shut down the Mac.On the built-in keyboard (this does not work from an external keyboard), simultaneously press and hold the left Shift, Control, and Option keys while you press the power button for at least 10 seconds. (If you have a MacBook Pro with Touch ID, the Touch ID button is also the power button.) Release all keys at the same time.Press the power button to start the Mac. Reset Mac Desktops and Notebooks With the Apple T2 Chip If you have an iMac Pro or MacBook Pro model from 2018 with the Apple T2 chip: Shut down the Mac.Press and hold the power button for 10 seconds.Release the power button and wait a few seconds.Press the power button again to turn on the Mac. As an alternative for the iMac Pro with T2 chip, you can: Shut down the Mac.Unplug the power cord.Wait 15 seconds.Plugin the power cord.Wait five seconds.Press the power button to turn on the Mac. As an alternative for the MacBook Pro with T2 chip: 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 them down 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. Mac Desktops (Mac Pro, iMac, Mac mini) Shut down the Mac.Unplug the Mac's power cord.Wait 15 seconds.Reconnect the Mac's power cord.Wait five seconds.Start your 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, you can 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 your problems, combine it with a PRAM reset. Although the PRAM works differently than the SMC, it can store a few bits of information that the SMC uses. If you're still having problems, run the Apple Hardware Test to rule out a defective component on your Mac.