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User profile for user: koagul8or
koagul8or Author
User level: Level 1
9 points

Cannot boot iMac - Suspected Hardware Issue

Hi Guys,


In summary, my iMac (late 2012) is not starting up and I would really appreciate some expert help! :)


Problem

On start-up, the following steps occur in a loop:

  • I hear the chime.
  • Apple logo appears.
  • Loading bar gets to approximately seventy-five per cent.
  • Error message displayed: 'Your computer restarted because of a problem. Press a key or wait a few seconds to continue starting up.'
  • Automatic reboot.


Suspicions

I suspect there are two problems:

  1. The hard drive boot and/or recovery partitions are corrupt because I can access the main data partition using Target mode and Single User mode. But the bigger problem I think is…
  2. There is also some other hardware problem that stops me using the other recovery modes or booting from a bootable USB stick. If this is the case, then I guess I just need to give up!


Hopes

My only hope is that there might be some additional steps I can perform in Single User mode to recover from this situation and this is where you come in. :)


All data is backed up so this is merely an attempt to see if I can recover the hardware and hopefully not have to throw this iMac away.


Still in Progress

I am still in the process of trying to run fsck via Single User mode, but I can’t see how this will help due to the suspected hardware issue above (#2) which stops me reinstalling the operating system, even if I can repair the hard drive.


Hardware

  • First thing I tried was unplugging all hardware apart from a keyboard to access start up key recovery options.
  • I also plugged in a mouse when required.
  • I tried plugging these into different USB sockets in case there was a problem with one of the sockets.
  • I also removed all memory and tried different combinations of memory sticks in different slots in case the memory or the slots were broken.
  • None of the above made any difference to the results.


Summary of Recovery Start-up Key Results

  • These modes succeed:
    • Reset NVRAM/PRAM
    • Single User mode
    • Verbose mode
    • Target mode.
  • These modes fail:
    • Boot to external drive
    • Recovery (local or network)
    • Safe mode
    • Diagnostics (local or network)


Here are the detailed results of attempting each of the available boot up options...


Reset NVRAM/PRAM (Option-Command-P-R)

  • Succeeds.


Single User Mode (Command-S)

  • I’m still investigating the available options including fsck.
  • Any advice would be appreciated.


Verbose Mode (Command-V)

  • Lots of output displayed in console, then the ‘Your computer restarted because of a problem.’ error is displayed and machine reboots.
  • I have a video of the console output which I have still to analyse to see if there are any clues there.
    • If anyone has any suggestions of what to look for that would be appreciated.
    • I suspect there is a key piece of information there but most of the output is meaningless to me.
    • I will report back once I have investigated but the last couple of entries logged are:
    • TODO


Target Mode (T)

  • Succeeds.


Boot to external drive / Start-up Manager (Option)

  • The boot manager screen appears.
    • After selecting a bootable drive (tested on another mac), the following occurs:
    • Apple logo appears.
    • Loading bar gets to approximately fifty per cent.
    • System hangs.
  • Have tried more than bootable disk but the result is always the same.


Recovery (Command-R)

  • Apple logo appears.
  • Loading bar gets to approximately fifty per cent.
  • System hangs.


Networked Recovery (Option-Command-R)

  • Enter Wi-Fi password.
    • This is because I unplugged all unnecessary hardware.
    • If I startup with ethernet cable, the results are the same apart from having to enter Wi-Fi password.
  • For a while I see a spinning globe and this message: ‘Starting internet recovery this may take a while.’
  • Apple logo appears.
  • Loading bar gets to approximately fifty per cent.
  • System hangs.


Safe Mode (Shift)

  • Apple logo appears.
  • Loading bar gets to approximately eighty per cent.
  • System hangs.


Networked Diagnostics (Option-D)

  • Enter Wi-Fi password.
    • This is because I unplugged all unnecessary hardware.
    • If I startup with ethernet cable, the results are the same apart from having to enter Wi-Fi password.
  • For a while I see a spinning globe and this message: ‘Starting internet recovery this may take a while.’
    • This was unexpected for the local diagnostic tool. I suspect because the recovery partition is not available.
  • Screen goes black and displays errors:
    • Error 0x8000000000000003, Cannot load EFI/Drivers/TestSupport.efi
    • Status 0x00000003
  • After a couple of minutes the system reboots and the ‘Your computer restarted because of a problem’ error is displayed.


Diagnostics (D)

  • Exactly the same as the networked version which was unexpected for the local diagnostic tool.


iMac 27″, macOS 10.15

Posted on Jun 3, 2021 12:55 AM

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User profile for user: CarlAVII
CarlAVII
User level: Community Specialist

Posted on Jun 3, 2021 7:16 PM

Hi koagul8or,


Thanks for posting your issue here! We understand you're experiencing issues starting up your Mac. You've done a great job troubleshooting the issue so far. Since you've been unable to boot into Apple Diagnostics or macOS Recovery, it is possible there's a hardware issue you'll need to get looked at by an Apple technician. We'd recommend getting in touch with them directly at Get Support.


We hope this issue gets resolved for you. All the best!

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User profile for user: CarlAVII
CarlAVII
User level: Community Specialist

Jun 3, 2021 7:16 PM in response to koagul8or

Hi koagul8or,


Thanks for posting your issue here! We understand you're experiencing issues starting up your Mac. You've done a great job troubleshooting the issue so far. Since you've been unable to boot into Apple Diagnostics or macOS Recovery, it is possible there's a hardware issue you'll need to get looked at by an Apple technician. We'd recommend getting in touch with them directly at Get Support.


We hope this issue gets resolved for you. All the best!

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User profile for user: Calvin_BT
Calvin_BT
User level: Level 3
663 points

Jun 7, 2021 5:53 PM in response to koagul8or

koagul8or wrote:

ummary of Recovery Start-up Key Results•
These modes succeed:
• Reset NVRAM/PRAM
• Single User mode
• Verbose mode
• Target mode.
• These modes fail:
• Boot to external drive
• Recovery (local or network)
• Safe mode
• Diagnostics (local or network)

Here are the detailed results of attempting each of the available boot up options...

Reset NVRAM/PRAM (Option-Command-P-R)•
Succeeds.

Single User Mode (Command-S)•
I’m still investigating the available options including fsck.
• Any advice would be appreciated.

Verbose Mode (Command-V)•
Lots of output displayed in console, then the ‘Your computer restarted because of a problem.’ error is displayed and machine reboots.
• I have a video of the console output which I have still to analyse to see if there are any clues there.
• If anyone has any suggestions of what to look for that would be appreciated.
• I suspect there is a key piece of information there but most of the output is meaningless to me.
• I will report back once I have investigated but the last couple of entries logged are:
• TODO

Target Mode (T)•
Succeeds.

Boot to external drive / Start-up Manager (Option)•
The boot manager screen appears.
• After selecting a bootable drive (tested on another mac), the following occurs:
• Apple logo appears.
• Loading bar gets to approximately fifty per cent.
• System hangs.
• Have tried more than bootable disk but the result is always the same.

Recovery (Command-R)•
Apple logo appears.
• Loading bar gets to approximately fifty per cent.
• System hangs.

Networked Recovery (Option-Command-R)•
Enter Wi-Fi password.
• This is because I unplugged all unnecessary hardware.
• If I startup with ethernet cable, the results are the same apart from having to enter Wi-Fi password.
• For a while I see a spinning globe and this message: ‘Starting internet recovery this may take a while.’
• Apple logo appears.
• Loading bar gets to approximately fifty per cent.
• System hangs.

Safe Mode (Shift)•
Apple logo appears.
• Loading bar gets to approximately eighty per cent.
• System hangs.

Networked Diagnostics (Option-D)•
Enter Wi-Fi password.
• This is because I unplugged all unnecessary hardware.
• If I startup with ethernet cable, the results are the same apart from having to enter Wi-Fi password.
• For a while I see a spinning globe and this message: ‘Starting internet recovery this may take a while.’
This was unexpected for the local diagnostic tool.• I suspect because the recovery partition is not available.
• Screen goes black and displays errors:
• Error 0x8000000000000003, Cannot load EFI/Drivers/TestSupport.efi
• Status 0x00000003
• After a couple of minutes the system reboots and the ‘Your computer restarted because of a problem’ error is displayed.

Diagnostics (D)
Exactly the same as the networked version which was unexpected for the local diagnostic tool• .

You were missing one thing:


Reset SMC (Shift+Option+Control)

  • Unplug your iMac power cord and wait for a few minutes.
  • Plug your iMac power cord and wait for more 5 seconds
  • Then turn it on
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User profile for user: HWTech
HWTech
User level: Level 9
60,284 points

Jun 3, 2021 7:46 PM in response to koagul8or

My first guess would be a failing hard drive as some failing hard drives can prevent booting from external media such as USB or Internet Recovery Mode. When booting into Verbose Mode look to see if there are any "I/O Errors" listed which would indicate a failing hard drive. If you don't see any "I/O Errors" listed, then I can provide you instructions for using a bootable Knoppix Linux USB stick to check the health of the hard drive unless you have a bootable macOS external drive (full macOS boot drive, not an installer). If you have a bootable macOS external drive, then you can use DriveDx to check the health of the internal drive(s). I don't know if DriveDx can access the health information from a drive on a Mac in Target Disk Mode.


Unfortunately Apple broke the online Apple Diagnostics for some systems when the system firmware was updated as evidenced by the "Cannot load EFI/Drivers/TestSupport.efi" error.


Thank you for the very nicely formatting of your post with the specific details.



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User profile for user: koagul8or
koagul8or Author
User level: Level 1
9 points

Jun 3, 2021 11:26 PM in response to HWTech

My first guess would be a failing hard drive as some failing hard drives can prevent booting from external media such as USB or Internet Recovery Mode.

That's interesting, I did not realise that.

When booting into Verbose Mode look to see if there are any "I/O Errors" listed which would indicate a failing hard drive.

I will definitely do that. I haven't bothered so far because I thought there was little point if I cannot boot to a bootable Mac installer. But your post suggests otherwise.

If you don't see any "I/O Errors" listed, then I can provide you instructions for using a bootable Knoppix Linux USB stick to check the health of the hard drive...

I can Google this unless you have some special sauce that I might not find on the web? :) I did try booting from a Linux Tails USB stick but that had the same results as noted above i.e. startup hangs after selecting the USB stick from the boot loader. However, I had never tried that Tails USB stick on the broken iMac before it broke, so I cannot be sure the iMac is the problem there.

..unless you have a bootable macOS external drive (full macOS boot drive, not an installer).

I might have actually, but did not think to try that because I did not think the result would be any different, thanks.

f you have a bootable macOS external drive, then you can use DriveDx to check the health of the internal drive(s). I don't know if DriveDx can access the health information from a drive on a Mac in Target Disk Mode.

I will give that a go thanks.

Unfortunately Apple broke the online Apple Diagnostics for some systems when the system firmware was updated as evidenced by the "Cannot load EFI/Drivers/TestSupport.efi" error.

That is a shame. I could have done with that because believe it or not, the hard drive on my MacBook Pro failed yesterday! But it's been working since 2010 so I can't complain. :)

Thank you for the very nicely formatting of your post with the specific details.

Thank you for saying so. The notes were mostly written for my own benefit since I had tried so many different fixes, I was beginning to forget what I had and hadn't tried.


I will update when I have any additional information. Thanks again!

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User profile for user: HWTech
HWTech
User level: Level 9
60,284 points

Jun 4, 2021 4:49 PM in response to koagul8or

koagul8or wrote:

If you don't see any "I/O Errors" listed, then I can provide you instructions for using a bootable Knoppix Linux USB stick to check the health of the hard drive...
I can Google this unless you have some special sauce that I might not find on the web? :) I did try booting from a Linux Tails USB stick but that had the same results as noted above i.e. startup hangs after selecting the USB stick from the boot loader. However, I had never tried that Tails USB stick on the broken iMac before it broke, so I cannot be sure the iMac is the problem there.

I don't know whether Linux Tails will boot a Mac. Macs can be a bit tricky. I do know that Knoppix v8.6.1 will boot most 2015 and earlier Macs (I haven't tried using the latest v9.x yet). When booting Knoppix the Mac may appear to be frozen on the Apple boot picker menu so you must give Knoppix lots of time to boot especially if there is a possibility of a drive failure which can slow things down. Make sure to choose an .iso image with "EN" in the name for "ENglish".

https://www.knopper.net/knoppix/index-en.html


Linux tends to have better luck booting a Mac with issues as Linux tends to get past any errors while macOS may get stuck on the errors. Plus Linux may use the hardware a bit differently which can allow Linux to boot past some issues and Knoppix does not try to mount any volumes until you ask Knoppix to mount them.


..unless you have a bootable macOS external drive (full macOS boot drive, not an installer).
I might have actually, but did not think to try that because I did not think the result would be any different, thanks.

It probably won't work either, but I offered that as an option since a lot of people think using Linux is too difficult. At least it will bypass any network issues or possible USB stick issues for a macOS USB installer.


Thank you for saying so. The notes were mostly written for my own benefit since I had tried so many different fixes, I was beginning to forget what I had and hadn't tried.

It is always good to keep notes when troubleshooting odd issues. It is amazing how quickly you can mix up things you notice. I'm guilty of thinking I'll remember and keep things straight, but it doesn't take much to get distracted and then confused.

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User profile for user: koagul8or
koagul8or Author
User level: Level 1
9 points

Jun 7, 2021 12:04 PM in response to HWTech

I took it into the Apple store over the weekend and they confirmed that the logic/motherboard is not functioning properly.


I wish I had taken it in sooner because it took five minutes for them to establish this, and I had spent many many hours trying to self-diagnose. :)


I think the only (economical) course of action is to wipe the hard drive and try to sell it for parts.


Thanks to everyone that took the time to try and help. If nothing else, I learned a couple of tricks which may come in useful if I ever find myself in this situation again. :)

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User profile for user: koagul8or
koagul8or Author
User level: Level 1
9 points

Jun 7, 2021 10:56 PM in response to Calvin_BT

Calvin_BT wrote:

Single-User-Mode is now useless since macOS Catalina increased their security. Mount and fsck commands won't work unless you turn off SIP in Recovery Mode

Nice one Calvin, that has saved me a lot of wasted time! :)

I could see the drive was mounted read-only, and was trying to find the correct combinations of commands to make it writeable.

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Cannot boot iMac - Suspected Hardware Issue

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