Mac Fixes

How to Run Apple Diagnostics

If you suspect that your Mac is repeatedly suffering from the same hardware issue, you should run diagnostics on Mac. This program is a built-in utility that Macs have had since 2013. Older Macs have a similar program called Apple Hardware Test.


Today, you’ll learn how to run MacBook Diagnostics and solve any potential problems you might be having. You’ll also find out how to fix problems that the Diagnostics tool reveals.

Before we start


Apple’s Diagnostics tool is excellent for identifying potential problems with your Mac. However, you’ll still need to do a lot of the manual work to solve the issue. MacKeeper’s Find & Fix solution will help you identify hardware discrepancies and automate the repair process.


Follow these instructions to use the Find & Fix solution:

  1. Download MacKeeper.
  2. Go to Find & Fix at the top of your screen.
  3. Select Start Full Scan.
  4. When the scan is complete, click on Fix Items Safely.
  5. You might need to review some items before they’re fixed. If that’s the case, you’ll see a Continue option; here, you can then review them.

What is Apple Diagnostics?

Apple Diagnostics is a tool installed by default on every modern Mac that can be used to detect various hardware errors, including:

  • Problems with power supply, battery, or power adapter
  • Graphics problems
  • Issues with logic board or CPU
  • Problems with USB and Bluetooth

Apple Diagnostics is free to use and can help you solve Mac running slow issues, in addition to MacBook fan making noise, your Mac overheating, and more.

Prepare your Mac before running a health test

To make sure that you’re ready to run a MacBook health check, prepare your device in advance. Do the following:

  • Ensure that you have an internet connection before starting an Apple Diagnostics test. This will allow you to get recommended support resources, upload the results to Apple, and get access to the Apple support webpage.
  • Eject and unplug external hard drives, iPhones, iPads, etc. However, you can keep your mouse, keyboard, and display plugged in.
  • When running Diagnostics on a MacBook Pro or another portable device, use a power adapter (AC power source). Testing may drain the battery and cause an unexpected shutdown.

How to start Apple Diagnostics

How you use Apple Diagnostics to test your Mac depends on your device’s chip. Below are the steps for Macs with M1, M2, or M3 chips—in addition to those with Intel chips.


Check out the corresponding guides:

Running Apple Diagnostics on M1, M2, or M3

Follow these instructions to perform the Mac diagnostics test on Apple Silicon computers:

  • Hold the standby button on your Mac.
  • Let go of the standby button when you see your list of startup options. Then, hold command + D.
  • Wait for your Mac to perform the diagnostics test.
  • Turn your device off by pressing Shut Down. Then, power your Mac on again like normal to start tackling the problem.
Run Mac Diagnostics by first holding the standby button. Your Mac will turn off, and you'll then have to enter Diagnostics after going into Safe Mode.
Step 1. Hold the standby button
To run Apple Diagnostics, you should press command + D on your keyboard. After doing that, you might need to change your language if asked.
Step 2. Press command + D on your keyboard
Wait for your Mac Diagnostics to run. A screen with a bar will appear and begin looking for different possible problems. The length of time this takes will depend on multiple factors.
Step 3. Wait for your Mac Diagnostics report

Starting Apple Diagnostics on Macs with Intel chips

Follow these steps to run Diagnostics if your Mac has an Intel chip instead:

  1. Turn on your Mac and press D on your keyboard.
  2. Wait until you see a loading bar. Then, commence by turning off your device and fixing the problem.

After Apple Diagnostics finishes, you’ll get one of the following two messages on the screen:

  • If your Mac works fine, you will see the No issues found message. If you still suspect problems with your Mac, you can run the test again just to be more certain.
  • If there are some issues with your Mac, then you’ll see a brief description of them, together with one or more reference codes and additional instructions. If so, write down these generated error codes. We’ll talk more about them later.

Running a system health check on old Mac versions

To run an Apple Hardware Test on old Macs, follow the instructions below:

  1. Go to Apple logo > Shut Down.
  2. Boot your Mac and hold the D key during the startup to get into the Mac system diagnostics mode.
  3. Press through the arrows and hit the Enter key to select a language.
  4. Run the test. You’ll need to click the Test button or Enter key. Before that, you can select Perform extended testing for a more thorough check-up.
  5. Write any error codes that you see.

How to interpret Apple Diagnostics error codes

The following codes are the same in Apple Hardware Test and Apple Diagnostics:

Error code


ADP000No issues found
CNW001 - CNW006Wi-Fi hardware problems
CNW007- CNW008No Wi-Fi networks detected
NDC001 - NDC006Camera issues
NDD001USB hardware issues
NDK001 - NDK004Keyboard issues
NDL001Bluetooth hardware issues
NDR001 - NDR004Trackpad problems
NDT001 - NDT006Thunderbolt hardware problems
NNN001No serial number detected
PFM001 - PFM007System Management Controller problems
PFR001Mac firmware issue
PPF001 - PPF004Fan problem
PPM001Memory module issue
PPM002 - PPM015Onboard memory problem
PPP001 - PPP003Power adapter issue
PPP007Power adapter not tested
PPR001Processor problem
PPT001Battery not detected
PPT002 - PPT003Battery needs to be replaced soon
PPT004Battery requires service
PPT005Battery not installed correctly
PPT006Battery requires service
PPT007Battery needs to be replaced soon
VDC001 - VDC007SD Card reader issues
VDH002 - VDH004Storage device issue
VDH005Can't start OS X recovery
VFD001 - VFD005Display issues encountered
VFD006Graphics processor problems
VFD007Display issues encountered
VFF001Audio hardware problems
4AIRAirport wireless card problems
4ETHEthernet issues
4HDDHard disk or SSD problems
4IRPLogic board problems
4MEMRAM problems
4MHDExternal disk issues
4MLBLogic board controller problems
4MOTFans problems
4PRCProcessor problems
4SNSSensor issues
4YDCGraphic card problems

Note from our experts: 


To stop your Mac from running energy-consuming processes that may hinder performance, use Activity Monitor on Mac.

What if Mac system check isn’t starting

Using a firmware password can prevent Mac diagnostics from starting. Therefore, you need to turn off the firmware password, and you can easily do so by following these steps:

  1. Start up your Mac and hold Command (⌘) + R to enter Recovery Mode.
  2. Enter your firmware password.
  3. Click Utilities from the menu bar and choose Firmware Password Utility/Startup Security Utility.
  4. Click Turn Off Firmware Password.
  5. Enter your firmware password.
  6. Restart your Mac.

How to fix Apple Diagnostics error codes

PRAM and NVRAM store system settings like volume, time zone, display resolution and brightness, startup disk selection, and many more. In contrast, SMC is a subsystem that controls your Mac’s temperature and power, batteries, hibernation, and sleep. Resetting the NVRAM, PRAM, or SMC often fixes Apple Diagnostics errors.


Read how to do that below:


Resetting the NVRAM/PRAM is much easier on an M1, M2, or M3 Mac than it is on a device with an Intel chip. Below are the steps you should follow for both.

How to reset NVRAM/PRAM on an M1, M2, or M3 Mac

If you want to reset the NVRAM or PRAM on your Mac with an Apple Silicon chip, simply turn your device off like normal. These processes will then reset. To ensure that your required changes take effect, you may want to wait 30-60 seconds before switching your device back on.

How to reset NVRAM/PRAM on a Mac with an Intel chip

If you’re using a firmware password, you first need to turn it off and follow the steps in What if Mac system check isn’t starting section. Then, move to resetting your NVRAM:

  1. Restart your Mac.
  2. Hold Option + Command (⌘) + P + R for about 20 seconds during booting.
  3. During these 20 seconds, your Mac might appear to restart. It’s completely fine.
  4. You can release the keys whenever you hear the startup sound, or when the Apple logo appears and disappears for the second time.

Hint from our team: Resetting your NVRAM can reset some of your settings, so you might need to go to System Preferences/System Settings to adjust any settings that were reset.

Reset SMC

Restarting your SMC depends on whether your Mac has an Intel, T2, or M1-M3 chip. If you have an M1, M2, or M3 chip, turning off your device and waiting 30 seconds—before switching it back on—should solve the process.


If you have a T2 or Intel chip, follow the instructions for your device below.

For laptop computers

Follow these instructions if your MacBook laptop has a T2 security chip:

  1. Shut down your Mac.
  2. Press and hold the power button for 10 seconds.
  3. Wait a few seconds before turning on your Mac.

For desktop computers

If you have a desktop Mac with a T2 security chip, you’ll need to follow these steps instead:

  1. Shut down your Mac. Then, unplug the power cord.
  2. Wait 15 seconds and then plug the power cord back in.
  3. Wait for five seconds and turn on your Mac.

If you don’t have a T2 chip, you can try one of the following methods.

For laptop computers with non-removable batteries

Follow these steps if your Mac doesn’t have a removable battery:

  1. Shut down your Mac.
  2. Press and hold the Shift + Control + Option + Power buttons for about 10 seconds.
  3. After holding for 10 seconds, release all keys and turn on your Mac.

For laptop computers with removable batteries

If your Mac has a removable battery, follow these instructions to reset your SMC:

  1. Shut down your Mac.
  2. Remove the battery (you can contact MacKeeper’s Premuim Services to get professional help with it).
  3. Press and hold the Power button for five seconds.
  4. Reinstall the battery.
  5. Turn on your Mac.

Reset SMC for desktop computers

For desktop computers without a T2 security chip, here are the instructions you should follow to reset your SMC:

  1. Shut down your Mac and unplug the power cord.
  2. Wait for 15 seconds and plug the power cord back in.
  3. Wait for five seconds, then turn on your Mac.

Our pro tip: 


In addition to running Diagnostics by turning off your device, it’s also possible to run wireless Diagnostics on your Mac.

Fix your big Mac problems with Apple Diagnostics

Apple Diagnostics is a simple way to reveal the most common Mac hardware problems. You can resolve many of the issues you see by resetting your SMC or NVRAM/PRAM.


Sometimes, however, Apple Diagnostics may say that no problems exist when there are issues. In these instances, you can use MacKeeper’s Find & Fix tool to solve any challenges you encounter. And even if you do find problems with Apple Diagnostics, Find & Fix will automate the reparation process.

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