Mar 29, 2019 Resetting a Mac's NVRAM can help fix errors in things like your battery's display, while battery settings can be reset if your Mac is frequently overheating or crashing. Restoring your MacBook Pro to its factory settings will erase everything on the hard drive and reinstall the operating system. How to reset the SMC, PRAM and NVRAM on an iMac Pro. I had to make a separate guide for this Mac as this Mac has the new T2 chip and requires a different.
What the SMC does
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
- Sudden Motion Sensor (SMS)
- 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
How to know if you need to reset the SMC
These symptoms might mean that an SMC reset is necessary:
- Your computer's fans run at high speed, even though it isn't under heavy usage and is properly ventilated.
- The keyboard backlight behaves incorrectly.
- The status indicator light, if present, behaves incorrectly.
- Battery indicator lights, if present, behave incorrectly on Mac notebooks with a non-removable battery.
- The display backlight doesn't respond correctly to ambient light changes.
- Your Mac doesn't respond when you press the power button.
- Your Mac notebook doesn't respond properly when you close or open the lid.
- Your Mac sleeps or shuts down unexpectedly and you can't turn it back on.
- The battery doesn't charge properly.
- Your MacBook or MacBook Pro doesn't charge through its built-in USB-C port.
- Your MacBook or MacBook Pro doesn't recognize external devices that are connected to its built-in USB-C port.
- The MagSafe power adapter LED, if present, doesn't indicate the correct charging activity.
- Your Mac performs unusually slowly, even though its CPU isn't under an abnormally heavy load.
- A Mac 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 turn on when you move the computer.
Before you reset the SMC
Try each of these steps in this order before you reset the SMC. Test the issue after each step to see if the issue still occurs.
- If your Mac isn't responding, press and hold the power button until it shuts down. You'll lose unsaved work in any open applications. Then press the power button again to turn on your Mac.
- Press Command-Option*-Escape to force quit any application that's not responding.
- Put your Mac to sleep by choosing Apple () menu > Sleep. Wake the computer after it's gone to sleep.
- Restart your Mac by choosing Apple menu > Restart.
- Shut down your Mac by choosing Apple menu > Shut Down, then press the power button again to turn on your Mac.
If you're using a Mac notebook that's having power or battery issues, follow these steps:
- Unplug the power adapter from your Mac and the electrical outlet for several seconds, then plug it back in.
- Choose Apple menu > Shut Down and wait for your Mac to shut down.
- Remove and re-insert the battery if it's removable.
- Press the power button again to turn on your Mac.
If the issue still isn't resolved, you might need to reset the SMC using the steps below.
* On some keyboards, the Option key is also labeled Alt.
How to reset the SMC on Mac notebooks
If your Mac notebook has the Apple T2 Security Chip, skip ahead to the T2 section.
To reset the SMC on a Mac notebook, first determine whether the battery is removable. Most older Mac notebooks have removable batteries. Mac notebooks that have nonremovable batteries 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:
- Choose Apple menu > Shut Down and wait for your Mac to shut down.
- Press Shift-Control-Option on the left side of the built-in keyboard, then press the power button at the same time. Hold these keys and the power button for 10 seconds. If you have a MacBook Pro with Touch ID, the Touch ID button is also the power button.
- Release all keys.
- Press the power button again to turn on your Mac.
If the battery is removable:
- Shut down your Mac.
- Remove the battery. If you need help removing the battery, contact an Apple Authorized Service Provider or Apple Retail Store.
- Press and hold the power button for 5 seconds.
- Reinstall the battery.
- Press the power button again to turn on your Mac.
How to reset the SMC on Mac desktop computers
If your Mac desktop computer has the Apple T2 Security Chip, skip ahead to the T2 section.
Follow these steps for iMac, Mac mini, Mac Pro, and Xserve.
- Choose Apple menu > Shut Down and wait for your Mac to shut down.
- Unplug the power cord.
- Wait 15 seconds.
- Plug the power cord back in.
- Wait 5 seconds, then press the power button again 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 press and hold the power button for 5 seconds.
How to reset the SMC on a Mac that has the Apple T2 Security Chip
Follow these instructions for Mac computers that have the Apple T2 Security Chip.
Mac desktop computers with the T2 chip
Try this first:
- Choose Apple menu > Shut Down and wait for your Mac to shut down.
- Press and hold its power button for 10 seconds.
- Release the power button, then wait a few seconds.
- Press the power button again to turn on your Mac.
If that doesn't resolve the issue, follow these steps:
- Choose Apple menu > Shut Down and wait for your Mac to shut down.
- Unplug the power cord.
- Wait 15 seconds.
- Plug the power cord back in.
- Wait 5 seconds, then press the power button again to turn on your Mac.
Mac notebook computers with the T2 chip
Try this first:
- Choose Apple menu > Shut Down and wait for your Mac to shut down.
- Press and hold the power button for 10 seconds.
- Release the power button, then wait a few seconds.
- Press the power button again to turn on your Mac.
If that doesn't resolve the issue, follow these steps:
- Choose Apple menu > Shut Down and wait for your Mac to shut down.
- Press and hold the right Shift key, the left Option key, and the left Control key for 7 seconds. Your Mac might turn on and show the Apple logo on its display. Keep holding those keys while you also press and hold the power button for another 7 seconds. If your Mac turned on when you first pressed the keys, it turns off at this point.
- Release all three keys and the power button, then wait a few seconds.
- Press the power button again to turn on your Mac.
Learn more
Resetting the SMC doesn't reset or otherwise change the contents of NVRAM or PRAM on Intel-based Mac models.
When your Mac starts acting up, you’ll probably run through some common troubleshooting procedures, such as restarting it, running Disk Utility, and perhaps performing a Safe Boot. Your repair repertoire should also include a couple of additional procedures that can occasionally eliminate otherwise inscrutable problems—zapping the NVRAM and resetting the SMC.
Zap the NVRAM (or PRAM)
Back in the day, the standard list of quick fixes for random Mac ailments always included “zap the PRAM.” The P in PRAM stood for parameter (the RAM was just RAM—random access memory), and it referred to a small amount of special, battery-backed memory in every Mac that stored information the computer needed before it loaded the operating system. If the values in this memory got out of whack for one reason or another, your Mac might not start up correctly, or might exhibit any of numerous odd behaviors afterward. So you could press a key sequence at startup to reset (or “zap”) the PRAM, returning it to default, factory values.
Modern Macs no longer use PRAM; they instead use something called NVRAM (NV for non-volatile). NVRAM serves approximately the same purpose as PRAM, but instead of storing a dozen or more pieces of information, it now contains just a few: your selected startup disk, speaker volume, screen resolution, time zone, and—if your Mac has crashed recently—details of the last kernel panic.
NVRAM corruption is fairly uncommon, but if your Mac seems to take forever to figure out which disk to boot from, if it starts up with the wrong screen resolution, or if you have weird audio problems (like there’s no sound whatsoever, or the menu bar’s volume control is grayed out), it doesn’t hurt to reset the NVRAM—it’s quick and harmless.
To reset your NVRAM, you use exactly the same procedure you once used to reset PRAM.
- Shut down your Mac.
- Press the power button, and as soon as you power up the laptop, hold down Command-Option-P-R.
- Keep holding down those keys for about 20 seconds. Then let go and allow your Mac to continue starting normally. If you have an older Mac that chimes at boot, hold down the keys until you hear a second startup chime.
- Then check the Startup Disk, Display, and Date & Time panes of System Preferences to make sure they’re set the way you want them.
If you hold down Command-Option-P-R at startup and you see nothing but a gray screen that doesn’t change for several minutes—no Apple logo, no progress bar, no second startup chime—don’t panic. The most likely cause is that your Mac isn’t registering the key presses due to wonkiness with a USB device. Disconnect all USB devices (except your keyboard, if it’s a wired keyboard), hold the power button down until the Mac shuts off completely, and then press it again and immediately hold down Command-Option-P-R.
2009 Mac Pro Manual Pram Reset Manual
If that doesn’t work and you’re using an external Bluetooth keyboard, try plugging in a USB keyboard instead. If you’re able to reset the NVRAM successfully with the wired keyboard, you can disconnect it and go back to your normal Bluetooth keyboard.
2009 Mac Pro Manual Pram Reset Download
Reset the SMC
Yet another component of your Mac’s hardware that stores crucial settings is the System Management Controller (SMC), a circuit that deals with power management, temperature monitoring and fan control, status lights, keyboard backlights, and a few other components. If your SMC becomes confused, you could experience problems like excessive fan noise, slow performance even though Activity Monitor doesn’t show the CPU being overtaxed, apps that take forever to launch, batteries that don’t charge correctly, problems with sleep or wake, and so on. (You can see a longer list on this Apple support page.) As with zapping the NVRAM, resetting the SMC to factory defaults may resolve these problems.
Apple says you shouldn’t reset the SMC without first trying other troubleshooting tasks, such as force-quitting problematic apps and restarting your Mac. However, Apple doesn’t mention any negative consequences of resetting the SMC, nor any way to determine for sure if the SMC is glitchy without resetting it and noticing that the problem went away. I’ve reset my Macs’ SMCs many times with no apparent ill effects, and on occasion that did in fact turn out to be the solution to a problem.
Before you can reset your SMC, you must shut down your Mac. After that, the procedure varies depending on the type of Mac you have.
Desktop Macs: Disconnect the power cord (either from the Mac or from the AC outlet). Wait 15 seconds and plug it back in. Then wait another 5 seconds and turn the Mac back on.
Portable Macs with non-removable batteries: Shut down and unplug your Mac. On the built-in keyboard, press and hold the Shift, Option, and Control keys on the left side and press the power button and hold all of these down for 10 seconds, then release the keys. Connect the power adapter and then turn the Mac on normally.
Portable Macs with removable batteries: Shut down your Mac. Disconnect the power cord and remove the battery. Press the power button, hold it for 5 seconds, and then let go. Put the battery back in, reconnect the power cord, and turn the Mac on normally.
Although neither of these procedures is a guaranteed cure, both of them can solve a number of odd problems, and are worth a few minutes of your time before hauling your Mac in to see the local Apple Genius.