Chosen Solution

Yesterday, I was working in Autodesk Maya, and suddenly whole screen went black, so I did a hardware reset, by holding down the power button. After that the iMac doesn’t boot properly. It does the chime sound, then the apple logo with indicator and then just goes to a white screen. The keyboard doesn’t work as caps-lock light wont come on. I have tried the following: RAM reset (Cmd+Opt+P+R)SMC reset (unplugged power source for 2-3 hrs, held down power button for 10 sec)Removed ram cards and powered up, it did the SOS beep with 5 second intervals, so I’m guessing logic board is fineHolding down Option key during startup brings up the disk selector (I have 2 partitions one with Lion and one with Mountain Lion) neither boots up.Tried booting from an external Mountain Lion Install USB drive, it shows up in Disk Selector, am able to select it, but then it stops at white screenRan a thorough Apple Hardware Test off the internet through ethernet cable, took 1:45 hours and it showed no errorsTried to run through Mountain Lion Recovery Disk, same white screenEntered sIngle user mode (Cmd+S) and ran fsck -fy on boot disk, it gave a few minor errors, so I repeated fsck -fy a few times until it no longer gave errors, still doesn’t get past white screen. I’m able to browse the HDD in single user mode using the shell. Then did “exit” and also “reboot” commands, both ended in white screen. I’ve looked around and found several guides dealing with this exact problem, but as you can see from the elaborate list above, none of those remedies have worked for me. Any help is greatly appreciated, I’m on a tight deadline to finish this animation project and this is the only machine I have access to at the moment. I don’t have Apple care nor warranty and there’s no Apple store/Genius Bar nearby.

Apparently this is a graphics card problem, Apple recalled it, see http://support.apple.com/kb/TS5167 I got mine replaced by Apple for free. Good luck!

Hi, I had the same problem on my iMac dual-core 3.06gHz. Stupidly I put in a firmware password and forgot it and I had recently blocked anybody accessing my CD drives etc. Even I was blocked. Therefore I couldn’t wipe the hard drive and reload OSX. I got the blank white screen. This method got my iMac back. To do this you need to alter your RAM configuration first by adding or removing memory. This forces the PRAM to take action. You will still need enough RAM to run the machine of course.

  1. After changing your RAM either up or down.
  2. Using a wired keyboard, start computer with keys COMMAND-OPTION-P-R pressed in. You MUST use the COMMAND-OPTION keys on the RIGHT side of the keyboard.
  3. Let the machine boot THREE times (mouse lights up on each boot cycle, turn it over to see)
  4. After the THIRD or FOURTH boot cycle hold the OPTION key down ONLY.
  5. A BOOT MENU should appear. I cannot remember if I hit EJECT on the boot menu or on the keyboard. Try each if it doesn’t work first time. You can access your CD drive now, put in your BOOT CD (OSX disk). Reboot into Single User mode and reload your OSX system. At step (5) You may not have to reload your system files, just set up your PRAM.

Same problem only my solution was to press on D while holding the power button until apple logo came up then the bar showing it was loading something. Afterward it worked fine.

Can you boot from an external HD or flash drive? If you can you will likely need to run Apples’ Disk Utility to straighten things up. I would strongly recommend clearing out some of the stuff you have on your disk as you likely ran out of space and/or have a highly fragmented HD. Try using Drive Genius or other good defragmenter app to defrag the HD. If you can’t boot with an external drive then your problem is not HD/OS related. But given the fact you can get the system to run and access the HD in single user mode I suspect its the HD that just needs attention.

Thx for writing this article - had the same problems. And actually repaired earliere iMacs 27. So have a bit of insight in the tech. But was getting grey hairs over this one, and wen’t through all possible scenarios (as you) then after two days found this o/ :) Thanks again, will contact Apple tomorrow.

i have got same issue and the problem is Graphic card. The solution have simple if u have a little electronic skills. teardown imac and remove the graphic card. and also remove gpu coller. your graphic card must be like this picture of gpu after that u must be very carefull this proses. first u clean gently with alcohol and toothbrush. after that u bake in oven like this video after that your graphic card work. this solution is riskly and get your own risk. your gpu has died also, maybe u can take it life back again

Ok… I had the white screen… and I tried everything… all the command this command that.. option this option that… and finally Command + S brought up a bunch of computer garble .. so I tried that fsck-fy and it said Bad Command … so I was like.. I don’t want to “exit”… so.. I typed “reboot” and wa-la the sum of a dog finally rebooted and I am back in business… unbelievable

Mine had this issue and it turned out to be a SMART failure on the hard drive.

Or you could just turn it over to apple and get its replaced for free :) https://support.apple.com/en-us/HT203787

Hi, I have a similar issue, with my imac 27" EMC 2546 from late 2012. The fusion drive was using the 3TB seagate baracuda that was under the apple recall, and it failed. However when it was failing and I was trying to boot from various other means, as from a usb stick, external drive or dvd, and it was only booting barely about 1/3rd of the way and stalling. Now with the whole fusion drive out (HDD&SDD) and a new blank seagate non apple drive in place (a 4TB), I get the same thing, and using a large number of methods to boot:

  • external HD (yosemite)
  • external HD in recovery mode (yosemite)
  • external HD in safe mode (yosemite)
  • external DVD installer disk (10.6 and 10.8)
  • off the net (netboot)
  • USB stick (10.6, 10.8 and 10.10)
  • USB stick in safe mode I can get it to boot in single user mode in any case, but nothing beyond that. I tried installing linux on that blank new drive and that worked fine and linux runs great on it. Running AHT, off the net, because I can’t get that to run from anything else, only shows the expected error from the missing temperature sensor on the hard drive, because it’s a genuine seagate non apple. So I expect all the system tests show nothing wrong with the machine, unless the AHT stops on the sensor error and doesn’t finish the remaining tests, which I would assume wouldn’t be the case. Resetting the pram hasn’t done anything, despite having done it many times. The SMC has been reste many times, at first by having the machine go to the local apple authorized store for the hard drive recall (I got the machine back because I didn’t want them to keep the original drive with my data on it). Everything seems to point to a healthy machine, although the missing firmware on the seagate drive causes the AHT error on the sensor, it runs linux just fine and it seems fine only until osx boots up to about 30% and stalls there. The only thing I could not try is to put it in target mode, because it has thunderbolt and not firewire, while I have an older laptop with firewire and not thunderbolt. I plan to locate a thunderbolt cable and ask someone I know to allow me to link up with their imac to see what I can do with the drive in that imac, but I suspect even if I managed to put a functional system on that drive, it won’t boot any further that in any other boot method. So what else could it be then???? I’m out of ideas.

hey! well there’s many different solutions and I had a problem related but I couldn’t figure it out so I went to this tech store for apple computers only and it’s not expensive and they will take any challenge and they will do it right then and there.

I’d turn off FileVault if enabled when troubleshooting this!