If the Apple hardware diagnostics test determines there is a problem and reports an error, you should write down the error code and any provided details (or take a picture of it with your iPhone) so that you can learn more about the problem. * If you are having trouble loading Apple Diagnostics can hold Option + D keys together to load the hardware test from the internet instead If no errors are found, the Mac hardware is good and the issue experienced is almost certainly software related, therefore backing up and reinstalling Mac OS X may be a reasonable troubleshooting next step*.If an error is found by the hardware diagnostics tool, this indicates there is a problem with some hardware on the Mac.The diagnostics tool will inform you if there is a problem found with the hardware:.If in Apple Diagnostics – let the “Checking your Mac” process run and complete.If in Apple Hardware Test – check the box for “Perform extended testing” and then click the “Test” button.Continue holding the “D” key until you see a progress bar (not the usual boot screen) – if the Mac is booting into Apple Hardware Test you will see a pixelated logo, if the Mac is booting into Apple Diagnostics you will see a simple progress bar or language selection screen instead.Shut down the Mac, then boot the Mac and at the moment the screen turns from black to grey, hold down the “D” key*.Disconnect all connected devices, drives, etc aside from a display / keyboard / mouse if applicable.Connect the Mac to a power source if you have not done so already.How to Run Apple Hardware Test on a Mac to Diagnose Hardware Problems Testing Apple hardware for troubles works the same on all Mac models, whether it’s an iMac, MacBook, MacBook Pro, MacBook Air, Mac Mini, or Mac Pro, and the version of Mac OS or Mac OS X on the computer does not matter. The appearances are slightly different as are the names, but the ability to test the hardware for problems is the same regardless of how things look or what they are called. Note that Apple Hardware Test runs on Macs built in 2013 and before, whereas newer Mac models will run Apple Diagnostics instead. The good news is that Apple Hardware Test can check to see if there are indeed hardware issues to look into, and you can run it yourself with just a little effort.

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