My MBP will no longer detect external displays. It was working fine a few hours ago at work, I got home and plugged in the external display as usual and turned on the machine and nothing. Using the "Detect Displays" does nothing. I have tried re-plugging the mini DVI display port adapter and have tried using a different monitor with a different monitor cable. I have tried shutting down and booting without the adapter plugged in and then plugging in the adapter. Nothing works. Is there some trick to force my MBP to see and use the external monitor?

More Information: When I plug in the display port the LCD screen goes blue for a moment. Checking the Graphics and Displays display connecter shows
Status: No Display Connected

  • To confirm the NVRAM reset did it for me - the laptop looked as if the connector on the board was faulty but I did this and everything is working perfectly.
    – user61178
    Commented Oct 31, 2013 at 12:52
  • I had the same problem, a simple restart fixed the problem for me.
    – Thomas K
    Commented Sep 13, 2016 at 7:11

2 Answers 2


I have had a similar problem (albeit with a Powerbook) and I had to change my DVI-VGA (back then we didn't have Mini-DP). It was working until one day it simply stopped working. Since I had a lot of displays at home, I tried -like you- different cables and displays to no avail until I found another adapter and boom, it worked.

Another way to test this is go to an App Store or similar with your machine and your cable. Try to make it work there. If it doesn't, they will have extra adapters to rule out that possibility. If a new cable, display, adapter also fails, then your Mini-DP port could be failing and that requires an App Store anyway…

  • It turned out to the the adapter cable, I purchased another one today and plugged it in and everything was fine. Strange the cable seemed to be more resilient.
    – Jason Yost
    Commented Apr 27, 2011 at 18:06
  • Glad to hear you fixed it. They look resilient but they are not :S Commented Apr 27, 2011 at 19:06

Try resetting the parameter RAM using these instructions

You can also try resetting the SMC using these instructions

  • 1
    This did not help, sorry
    – Jason Yost
    Commented Apr 27, 2011 at 2:48
  • Can you confirm that the monitor still works with another computer?
    – robzolkos
    Commented Apr 27, 2011 at 2:57
  • I have tried with a completely different monitor and cable that I am sure is working.
    – Jason Yost
    Commented Apr 27, 2011 at 3:00
  • ok cool. Check my edited answer re resetting the smc. See if that works.
    – robzolkos
    Commented Apr 27, 2011 at 3:02

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