iMac will not boot into diagnostics mode.

Question

iMac will not boot into diagnostics mode.

I have a Mid 2011 iMac. It developed a flickering screen that resolved within a couple of seconds but within a few minutes the screen went black. I turned the computer off and rebooted. It was slower to boot, didn't seem to be making all the usual noises on bootup, and now is very slow to start apps and perform tasks. The screen has had a couple of intermittent issues updating/refreshing/filling in the entire image. So I have tried to boot into into diagnostics mode by holding down the D key while the screen is still black and before the gray screen appears. It take a long time to boot but will not start up in diagnostic mode. It goes directly into Mavericks.

So what gives? Is there anything I can do before taking it to the "Genius" bar at the Apple store?

iMac 27"-OTHER, OS X Mavericks (10.9.5)

Posted on Jul 27, 2015 5:57 PM

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Answer 1

Best reply

SeaPapp

Level 7

26,486 points

Jul 27, 2015 6:05 PM in response to Fred-Norfolk, VA

Try this

1) SHUT DOWN the computer (Don't RESTART... shut it down)

2) Hold down the OPTION + D keys

3) Press the Power Button (make sure to hold down the OPTION + D keys first)

4) Continue to hold down the OPTION + D keys until the system enters AHT mode

5) Let the app verify the hardware setup before initiating the test.

6) There are two testing modes. To select the "Extended Test" activate the check box below the Test button.

7) Press Test button to begin test

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Answer 2

Jul 27, 2015 6:15 PM in response to SeaPapp

I think the AHT mode is for newer Macs than mine, but I'll give it a try.

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Answer 3

Jul 27, 2015 8:19 PM in response to SeaPapp

Thanks. It worked. It didn't discover any hardware problems, but something was glitching out. I'd never seen the computer behave like that before. Thanks for your help.

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Answer 4

SeaPapp

Level 7

26,486 points

Jul 28, 2015 3:33 AM in response to Fred-Norfolk, VA

You might try booting into Safe Mode to see if that corrects anything. Try safe mode if your Mac doesn't finish starting up - Apple Support

Once it's completely booted up you can shut down and restart normally.

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Answer 5

Jul 28, 2015 4:57 AM in response to SeaPapp

I noticed that one of the things safe mode does is "disable user installed fronts." I did install a couple of free online fonts the other day because I had something very specific I wanted to use them for. Can fonts cause problems that might otherwise seem to be related to a graphics processor?

Regardless, I'll try booting into safe mode. Wasn't even aware Mac computers had a safe mode option.

BTW, a 7-year-old iMac I owned died a couple of weeks ago and I was hoping to wait until Apple put out some newer iMacs with 3.1 USB ports before replacing it. Does anyone know when in the year Apple normally releases updated iMacs?

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