My MacBook Pro A1708 is recovering from water damage.

From not working it has since been cleaned and have the LVDs Cable replaced.

Currently the display is showing black but I am able to connect to an external display.

If possible I would like to run Apple Diagnostics through an external monitor if anyone can help?


Follow these steps exactly:

  • Start your computer with external screen plugged in and an external keyboard, typically a USB keyboard
  • Once your screen is started, close its lid, it will go to sleep
  • On your USB keyboard, type a key. It will wake up, but now using external display as its main display
  • Instruct it to restart
  • Hold D on external keyboard when it chimes

The solution I eventually found was the following.

Turn on Mac while HDMI is connected to External Monitor Hold D till Mac is on Close Mac Screen Diagnostics will show on External Monitor

Hope this can be some assistance to you.

  • 1
    Can you add a link to the source for that quote? – grg Jan 4 '18 at 12:12

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