To start using Apple Diagnostics or AHT, first turn off any firmware password if you're using one. Next, shut down your Mac, disconnect all external devices except keyboard, mouse, display, and ...

How to Use Apple Diagnostics on an Intel Mac Press the power button to turn on your Mac, then immediately press and hold the D key on your keyboard as your Mac starts up.

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 ...