Use Apple Diagnostics to Troubleshoot Your Mac

In 2013, Apple changed its testing software for its Mac lineup. 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 Availability

Apple Diagnostics is included on every 2013 or later Mac. It's installed on the original startup drive and invoked using a ​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 version can be used if you replaced or reformatted the original startup drive, which erases 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

AD is for Mac models from 2013 and later. If your Mac is an earlier model, follow the previously mentioned Apple Hardware Test or AHT over the Internet.

1. Disconnect any external devices connected to your Mac, including printers, external hard drives, scanners, iPhones, iPods, and iPads. 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.

2. Write down the name of the wireless network and the password you use to access it if you use a Wi-Fi connection to the internet.

3. Shut down your Mac. If you're unable to shut down using the normal shutdown command under the Apple menu, press and hold the Power button until your Mac turns off.

After your Mac turns 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. Still, if you have one, you can access the Apple help system, which includes diagnostics notes based on AD error codes that may be generated.

Starting the Test

Here's what you need to do to run the Apple Diagnostics 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, enter the information you wrote down earlier to connect to your Wi-Fi network.

5. Wait. Apple Diagnostics displays a Checking Your Mac message, along with a progress bar. AD takes 2 to 5 minutes to complete.

6. AD displays a brief description of any issues uncovered, along with a corresponding error code. Write down any error codes that are generated and 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 that shows options for repairing or servicing your Mac.

1. Click the Get Started link to continue to the Apple support site.

2. Your Mac restarts using macOS or OS X Recovery, and Safari opens to the Apple Service & Support web page.

3. Click the Agree to Send link to send the AD error codes to Apple (no other data is sent).

4. View the additional information about the error codes that the Apple Service & Support page shows and the options you can take to resolve the problems.

5. If you would rather shut down or restart your Mac, press S (Shut Down) or R (Restart). If you want to rerun the test, press the Command+R keys.

Apple Diagnostics Error Codes

Compare any error codes that resulted from running Apple Diagnostics with this list:

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 software issues.