Apple has provided testing software for its Mac lineup for about as long as I can remember. However, over time the test suite has undergone changes, been updated, and advanced from being included on a special CD, to being able to perform the tests over the Internet.

In 2013, Apple changed the testing system once again. Abandoning the older Apple Hardware Test (AHT), and AHT over the Internet, Apple moved on to Apple Diagnostics, to help users find out what might be wrong with their Macs.

Although the name has changed to Apple Diagnostics (AD), the purpose of the app has not. AD can be used to find problems with your Mac’s hardware, including bad RAM, issues with your power supply, battery, or power adapter, failed sensors, graphics problems, issues with the logic board or CPU, wired and wireless Ethernet problems, internal drives, bad fans, camera, USB, and Bluetooth.

Apple Diagnostics is included on every 2013 or later Mac. It’s installed on the original startup drive, and invoked using a special keyboard shortcut when booting up the Mac.

AD is also available as a special boot environment that is downloaded over the Internet from Apple’s servers. Known as Apple Diagnostics over the Internet, this special version can be used if you have replaced or reformatted the original startup drive, and thus erased the AD version that was included at the time of purchase. The two forms of AD are for all purposes identical, although AD over the Internet involves a few extra steps to launch and use.

Using Apple Diagnostics

  1. Start by disconnecting any external devices connected to your Mac. This includes printers, external hard drives, scanners, iPhones, iPods, and iPads. In essence, all peripherals except the keyboard, monitor, wired Ethernet (if that is your primary connection to your network), and mouse should be disconnected from your Mac.
  1. If you’re using a Wi-Fi connection to the Internet, be sure to write down the access information, specifically, the name of the wireless network and the password you use to access it.
  2. Shut down your Mac. If you’re unable to shut down using the normal shutdown command under the Apple menu, you can press and hold the power button until your Mac turns off.

Once your Mac is turned off, you’re ready to start Apple Diagnostics, or Apple Diagnostics over the Internet. The difference between the two is the keyboard command you use at startup, and the need for an Internet connection to run AD over the Internet. If you have AD on your Mac, that’s the preferred version of the test to run. It doesn’t require an Internet connection, although if you have one, you’ll be able to access Apple’s help system, which includes diagnostics notes based on AD error codes that may be generated.

Let’s Start the Test

  1. Press your Mac’s power button.
  2. Immediately hold down the D key (AD) or option+D keys (AD over the Internet).
  3. Continue to hold down the key(s) until you see your Mac’s gray screen change to Apple Diagnostics.
  4. If you use a wireless connection, you’ll be asked to connect to your Wi-Fi network, using the information you wrote down earlier.
  1. Apple Diagnostics will begin with your screen displaying a Checking Your Mac message, along with a progress bar.
  2. Apple Diagnostics takes 2 to 5 minutes to complete.
  3. Once complete, AD will show a brief description of any issues uncovered, along with an error code.
  4. Write down any error codes that are generated; you can then compare them with the error code table below.

Finishing Up

If your Mac generated errors during the AD test, you can send the codes to Apple, which will result in an Apple support page being displayed, showing options for repairing or servicing your Mac.

  1. To continue to the Apple support site, click the Get Started link.
  1. Your Mac will restart using OS X Recovery, and Safari will open to the Apple Service & Support web page.
  2. Click the Agree to Send link to send the AD error codes to Apple (no other data is sent).
  3. The Apple Service & Support web site will show additional information about the error codes, and the options you can take to resolve the problems.
  4. If you would rather just shut down or restart your Mac, simply press S (Shut Down) or R (Restart). If you would like to rerun the test, press the command+R keys.

Apple Diagnostics Error Codes

AD Error Codes
Error Code Description
ADP000 No issues found
CNW001 – CNW006 Wi-Fi hardware problems
CNW007- CNW008 No Wi-Fi hardware detected
NDC001 – NDC006 Camera issues
NDD001 USB hardware issues
NDK001 – NDK004 Keyboard issues
NDL001 Bluetooth hardware issues
NDR001 – NDR004 Trackpad problems
NDT001 – NDT006 Thunderbolt hardware problems
NNN001 No serial number detected
PFM001 – PFM007 System Management Controller problems
PFR001 Mac firmware issue
PPF001 – PPF004 Fan problem
PPM001 Memory module issue
PPM002 – PPM015 Onboard memory problem
PPP001 – PPP003 Power adapter issue
PPP007 Power adapter not tested
PPR001 Processor problem
PPT001 Battery not detected
PPT002 – PPT003 Battery needs to be replaced soon
PPT004 Battery requires service
PPT005 Battery not installed correctly
PPT006 Battery requires service
PPT007 Battery needs to be replaced soon
VDC001 – VDC007 SD Card reader issues
VDH002 – VDH004 Storage device issue
VDH005 Can’t start OS X Recovery
VFD001 – VFD005 Display issues encountered
VFD006 Graphics processor problems
VFD007 Display issues encountered
VFF001 Audio hardware problems

It’s possible that the AD test won’t find any issues, even though you’re having problems you believe are related to your Mac’s hardware. The AD test is not a complete and comprehensive test, although it will find most of the common issues associated with hardware. If you still have problems, don’t rule out such common causes as failing drives or even software issues.

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