Use Apple Diagnostics on your Mac
Apple Diagnostics is a tool you can use to diagnose problems with your computer’s internal hardware, such as the logic board, memory and wireless components. You may be able to start your Mac with Apple Diagnostics, even if it doesn’t start using macOS.
To use Apple Diagnostics, follow the instructions in the Apple Support article Use Apple Diagnostics to test your Mac.
You may want to print the instructions before you begin. Choose File > Print, then click Print.
If Apple Diagnostics reports that your Wi-Fi card is not working properly, contact Apple Support or take your Mac to an Apple Store or Apple Authorised Service Provider.
To change the language, press Command-L.
Apple Diagnostics doesn’t check external hardware components, such as USB, or non-Apple devices, such as PCI cards from other vendors. It doesn’t check for operating system (macOS) or software-related problems such as app or extension conflicts.
If a hardware problem isn’t detected, there may be a problem with the version of macOS you’re using and you may need to reinstall it. See Reinstall macOS.