After isolating an issue on your Mac to a possible hardware issue, you can use Apple Diagnostics to help determine which hardware component might be causing the issue. Apple Diagnostics also suggests solutions and helps you contact Apple Support for assistance.
If your Mac was introduced before June 2013, it uses Apple Hardware Test instead.
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On your Mac, choose Apple menu Restart, then press and hold the D key while your Mac restarts. When the Apple Hardware Test chooser screen appears, select the language you want to use, then press the Return key or click the right arrow button. If you don’t see the chooser screen, Apple Hardware Test may not be available on your Mac.
If you choose to get more information, your Mac starts up from macOS Recovery and displays a web page asking you to choose your country or region. Click ”Agree to send” to send your serial number and reference codes to Apple. Then follow the onscreen service and support instructions. When you're done, you can choose Restart or Shut Down from the Apple menu.
This step requires an Internet connection. If you're not connected to the Internet, you'll see a page describing how to get connected.
If holding down the D key at startup doesn't start Apple Diagnostics: