Kernel_task major CPU usage


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kernel_task major CPU usage

Not long ago I bought a used 2019 iMac desktop and since doing a fresh reinstall of MacOS activity monitor is telling me that kernel_task is taking up 300%+ of my CPU at all times. This, as you might imagine, is throttling speeds terribly making the Mac near unusable. Common issues I’ve seen when trying to diagnose it all tend to suggest overheating issues but the device is running at a very normal temperature but with the fans blowing heavily. I tried to lower the fan speed with the “Macs Fan Control” App, which only made it so that fans were not so harsh but did nothing for the kernel_task issue.

I’m running a fresh install of macOS Monterey, but also had the same issue when I was on a version of Mojave when I first bought the system. I’ve also tried the fixes recommended like resetting the SMC and NVRAM. Anyone got any ideas on what the issue could be before I have to take the last resort of getting it repaired.
Thanks
 
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Cory Cooper

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Hello and welcome.
  • Which model: iMac (Retina 4K, 21.5-inch, 2019) or iMac (Retina 5K, 27-inch, 2019)?
  • Was the iMac ever repaired/opened to your knowledge?
  • Have you tried running Apple Diagnostics?
C
 
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Apple diagnostics returned Reference Code PFM006, I'm told to reset the SMC.
I've already reset the SMC before the diagnostics and have just reset it again afterwards to no avail.
 
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I'm much more proficient with Windows computers than I am with Macs but with a Windows computer, these kinds of problems are often due to a bad driver or a driver conflict. Is there a Safe Mode equivalent with Macintosh that would allow you to boot and bypass drivers?
 
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I'm much more proficient with Windows computers than I am with Macs but with a Windows computer, these kinds of problems are often due to a bad driver or a driver conflict. Is there a Safe Mode equivalent with Macintosh that would allow you to boot and bypass drivers?
Yes, the macOS equivalent is Safe Boot. On intel Macs, you simply have to boot up while holding down the Shift key. On M1 Macs, Safe Boot can be initiated from Recovery.
 
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kernel_task major CPU usage

Not long ago I bought a used 2019 iMac desktop and since doing a fresh reinstall of MacOS activity monitor is telling me that kernel_task is taking up 300%+ of my CPU at all times. This, as you might imagine, is throttling speeds terribly making the Mac near unusable. Common issues I’ve seen when trying to diagnose it all tend to suggest overheating issues but the device is running at a very normal temperature but with the fans blowing heavily. I tried to lower the fan speed with the “Macs Fan Control” App, which only made it so that fans were not so harsh but did nothing for the kernel_task issue.

I’m running a fresh install of macOS Monterey, but also had the same issue when I was on a version of Mojave when I first bought the system. I’ve also tried the fixes recommended like resetting the SMC and NVRAM. Anyone got any ideas on what the issue could be before I have to take the last resort of getting it repaired.
Thanks
Seems to me like you have an errant system extension which survived the transition from Mojave to Monterey. The question is whether the extension was user installed or part of macOS. If your installation of Monterey was not a “clean” installation, meaning it was an update on top of the old system (Mojave), some parts of the old system could have been carried over into the new and can be the source of conflict.

If I were dealing with this, I would just plan on completely erasing the drive and doing a fresh installation of Monterey. Of course I would not start until I know I have at least two Time Machine backup drives, and maybe at least a clone of the existing startup drive.

From recovery, I would use Disk Utility to erase and reformat the drive, then install macOS 12. I think the current version is 12.1. After the installation, you can migrate your data from Time Machine. So, unless the cause of your problem is hardware-related, you should be good—unless the problem is from an errant user extension or app setting, in which case it will be reinstalled with the migration.

I would elect to create a new user first, and test how the system runs. If everything looks good, you can proceed with migrating your previous user data. Don’t delete the new user. If the problem returns when you log into your old account then chances are, your system overload is coming from your user data. You may want to make the new user your permanent account instead and copy your older information as you need them.

In summary, (1) do the Time Machine backups; if not possible because of the system overload, do the backup in Safe Mode. (2) Boot into Recovery, launch Disk Utility and erase the startup drive. Erase at the top (device) level, deleting all containers and volumes. (3) Install macOS. Recovery should default to macOS Monterey. (4) Startup and create a new user… following the above procedure.

I forgot to mention also that if you can, create your second user account (also admin) before anything else. If you can restart and log into the new user account and no system overload happens, then you will know that the problem is coming from your older user data. But my bet is on a bad kext file in /System/Library/Extensions which will be difficult to pinpoint and can only be solved by a clean installation of macOS.
 
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OP stated he is running a "fresh" install of Monterey.

If the problem disappears in Safe Boot, is there a way to disable Kexts one at a time until you find the offender like you can with drivers in Windows? Also, sometimes in Windows just booting into Safe Mode will fix the problem. It must give the drivers an opportunity to resort themselves or something if too were in conflict.
 
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OP stated he is running a "fresh" install of Monterey.

If the problem disappears in Safe Boot, is there a way to disable Kexts one at a time until you find the offender like you can with drivers in Windows? Also, sometimes in Windows just booting into Safe Mode will fix the problem. It must give the drivers an opportunity to resort themselves or something if too were in conflict.
Have you looked inside the extensions folder (/System/Library/Extensions)? There are literally hundreds of .kext files in there, along with about a hundred or more bundles. Are you thinking of opening and inspecting each of those? A lot of the file names are very cryptic, at least to regular users like me. And who knows what will happen if you start removing those files from their folder, what, one at a time, or in batches?

I think it will be easier to do a clean install of macOS in order to have a fresh set of system files to start from.

Doing a Safe Boot can repair a lot of issues because part of the process involves clearing caches and performing disk checks (fsck). It’s what I usually run when weird things start to develop in my Mac, along with the usual parameter RAM (PRAM) reset, system management controller (SMC) reset, Spotlight reset, etc. A valuable tool, as well, is Activity Monitor, although a lot of the process names on the list are hard to decode.

As always, troubleshooting your Mac can be very gratifying from all the things you can learn from it. As an alternative to going through Recovery to reinstall the system, you can keep a copy of the latest macOS installer or combo updater. Running them, in Safe Mode, or from an attached bootable volume, will probably fix the majority of your system problems.
 

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