Usage of Apple Hardware test and Apple Diagnostics on Mac?

How to launch and use Apple's built-in hardware diagnostic tools, such as Apple Hardware Test and Apple Diagnostics?

Apple computers are well known for their stability and performance, also the usage of hardware resources. A lot of people are stating, that Mac computers never crashes, however there always is a chance of hardware or software crash. In order to help their users, Apple included built-in diagnostic tools, that checks all computer's components and display the results and recommendations how to solve existing issues. This tool, that provides multiple diagnostic tests were named Apple Hardware Test on all Mac computers released until 2013, later they slightly changed the name and appearance, on all models released after 2013 it was called Apple diagnostics.

Releasing the newer version of diagnostic tool, the developers attached error codes to the report about existing errors, that helps when you're trying to find possible solutions. By launching this tool you will be able to find out if your hard disk drive is failing or any memory faults, as well as video graphic card (GPU) and processors (CPU) performance, even the whole motherboard and additional modules, such as network, Bluetooth adapters, even the work of fans will be scanned for a possible errors. Also the diagnostic tool might give a hand while you're experiencing some issues and some software solutions couldn't help, by scanning whole computer you will be sure if the problem is within hardware or software. Knowing the troublemaker will allow to seek for more accurate solutions to your particular issue. In this article we will describe how to launch both the Apple Hardware Test and Apple Diagnostics on Mac computer.


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Launch built-in diagnostic tool on Mac

The method to launch Apple Hardware Test and Apple Diagnostics is same on all Mac computers, whether it is a desktop version, such as iMac, Mac mini, or Mac Pro, or portable version, such as MacBook, MacBook Pro, or MacBook Air.

  1. To launch diagnostic tool on your computer begin with connecting it to power source.
  2. Next step would be to disconnect all peripherals, such as external drives, multiple monitors, speakers and some any other, keyboard, mouse and main display may stay connected. 
  3. Once you're ready, shut down your computer, then turn it back on while holding down the D key. Keep holding until you see a progress bar or language selection, if you're launching the Apple Hardware Test you will see a pixelated Apple logo, while booting Apple Diagnostics you may see a simple progress bar or language selection window.
  4. If you've launched Apple Hardware Test enable the check box next to Perform extended testing and then click the Test button. On Apple Diagnostics let the Checking your Mac to run and complete.
  5. Once tool finishes scanning your computer, it will display a report about results, in case any issues were found it will show information about it, also if you're running Apple Diagnostics, there will be an error code together with other information about existing issue.
  6. Otherwise the report will state, that none issues were found and if you're still having any troubles, the problem will be within the software. In this case the easiest way to solve the existing problem would be to backup your operating system or perform a complete reinstall of Mac OS.


If you're struggling to launch diagnostic tool following this path, hold down Option and D instead, while starting Mac, this way it will boot diagnostic tool from the Internet instead of computer's hard disk. However, bear in mind, that without a proper Internet access this method will not work.

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Most common error codes of Apple Hardware Test report

If tool were able to find any issues with your Mac's hardware, the report will display an error code related to some particular hardware, in order to find the most accurate solution it is recommended to take a note of code or picture with your mobile device. In the list bellow you will find codes that displays an Apple Hardware Test tool.

List of error codes and related hardware:

  • 4AIR - AirPort wireless card
  • 4ETH - Ethernet
  • 4HDD -  Hard disk (includes SSD)
  • 4IRP -  Logic board
  • 4MEM - Memory module (RAM)
  • 4MHD - External disk
  • 4MLB - Logic board controller
  • 4MOT - Fans
  • 4PRC - Processor
  • 4SNS - Failed sensor
  • 4YDC - Video/Graphics card

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Error codes displayed within Apple Diagnostics report

In case you're using Apple Diagnostics the error codes will be different, what is more there might be few similar codes announcing about hardware's issues. In the table below you will find all error codes and description published by Apple.

Issue description Error code
Issues was not found. ADP000
Issues related to Wi-Fi hardware CNW001, CNW003, CNW004, CNW005, CNW006
Wi-Fi network was not detected, no available networks detected or hardware is not working CNW007, CNW008
Issues related to built-in camera NDC001, NDC003, NDC004, NDC005, NDC006
USB hardware related issues NDD001
Keyboard related issues NDK001, NDK003, NDK004
Issues related to Bluetooth hardware NDL001
Trackpad related issues NDR001, NDR003, NDR004
Issues related to Thunderbolt hardware NDT001, NDT002, NDT003, NDT004, NDT005, NDT006
Unable to detect a serial number NNN001
System Management Controller (SMC) related issues PFM001,PFM002, PFM003, PFM004, PFM005, PFM006, PFM007
Computer's firmware related issues PFR001
Fan related issues PPF001, PPF003, PPF004
Issues related to memory module PPM001
Issues related to onboard memory PPM002, PPM003, PPM004, PPM005, PPM006, PPM007, PPM008, PPM009, PPM010, PM011, PPM012, PPM013, PPM014, PPM015
Power adapter related issues PPP001, PPP002, PPP003
Unable to test power adapter PPP007
Issues related to processor (CPU) PPR001
Unable to detect battery PPT001
It is recommended to replace battery, because it is functioning normally, but holds less charge. PPT002, PPT003
Battery needs to be serviced PPT004, PPT006
Battery was not installed properly PPT005
Replace battery PPT007
Issues related to SD card reader VDC001, VDC003, VDC004, VDC005, VDC006, VDC007
Issues related to storage device VDH002, VDH004
Inaccessible macOS Recovery mode VDH005
Issues related to display VFD001, VFD002, VFD003, VFD004, VFD005, VFD007
Graphic processor (GPU) related issues VFD006
Audio hardware related issues VFF001


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