How to use Apple Diagnostics to identify Mac hardware problems

Hint: You probably want to see "ADP000"

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Apple’s Macs are usually pretty reliable, but when they do go wrong the Apple Diagnostics tool should help you figure out if you have a software or a hardware problem, but you need to know a few things to understand what it says.

What is Apple Diagnostics?

Apple Diagnostics is designed to put your hardware through a variety of tests designed to detect power supply, battery, graphics, logic board, USB and a huge range of other potential problems. While this test doesn’t cover every eventuality, it’s very good at identifying the most frequent hardware problems you can get using a Mac. You access these tests using a keyboard shortcut when you startup your Mac. They are also available via the Internet.

How do I launch Apple Diagnostics?

When launching Apple Diagnostics you should disconnect all peripherals with the exception of the keyboard, mouse, monitor and Ethernet (if used). You should also make sure you have the name and password for your Wi-Fi network if that’s how you get online.

Shut down the Mac and restart as follows: Start up and immediately hold the D key. Or depress the Option-D keys to access the tools online. Keep holding those keys down until Apple Diagnostics appears, once you get online the test will begin. A Checking Your Mac progress bar will appear for the duration of the test, which takes up to five minutes. When the test is complete any issues will be described and error code(s) displayed.

Also read: A Mac tech support handbook

How do I use Apple Diagnostics information?

You can send any error codes you receive to Apple using the Get Started link that appears. If you choose to do so your Mac will restart in OS X Recovery and Safari will launch Apple’s support pages. You can send the error codes to Apple to access details about these problems and how to repair them.

If you want to restart your Mac just press the R key (or S to Shut Down).

What is the most important Apple Diagnostics code?

The diagnostics code every Mac user should want to see is ADP000. It means no issues have been found. That’s good news as it suggests the problem you may be experiencing is not hardware-based. You should be dancing.

What are the other most useful Apple Diagnostics codes?

I’ll be honest, there are plenty of these codes – you’ll find a complete list right here at Apple Support, but here are ten to get started with:

CNW001-CNW006: Wi-Fi hardware problems (or CNW007-CNW008, which means now Wi-Fi hardware has been detected, which may also be a problem if you think you have such hardware).

NDD001: USB hardware isues (NDL001 indicates Bluetooth hardware problems).

PFR001: Mac firmware problem

PPF001-PPF004: Fan problem.

PPR001: Processor problem

VFD001-VFD005: This is the one that I’ve seen most often, it means “Display issues” have been identified.

VFD006: Graphics processor problem

VFD007: Display issues

VDH005: Cannot launch OS X Recovery

What should I do next?

If you have an identified hardware issue then the best thing you can do is use this system to make a call to Apple Support, as that’s a good way to find out more about the problem (even if you can’t afford to fix it immediately).

You may have expected to find a hardware problem but none has been found. This could be good news as it suggests OS X Recovery will be able to patch most common problems – just launch Disk Utility from within that petition and fix your disk. When that doesn’t seem to help you may need to reinstall your system (I hope you have backup). While this sounds like a great deal of hassle, don’t be too down hearted – even if you do have to replace the OS and reinstall all your digital stuff, this is still much cheaper than a full hardware repair.

May all your problems be software-based and easily rectified.

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