Resolved High kernel_task CPU usage on Macbook Pro 8.2


macrumors newbie
Original poster
May 12, 2004

An observation for those who might have trouble:

Today, my new Macbook Pro decided to run everything at 1/10th the speed of normal and kernel_task would eat between 4-600% CPU for a few seconds.

It would do so very distinctively after a few seconds of high CPU activity, such as scrolling a heavy webpage.

Another sign was that I was playing Half Life 2 for a few hours, and while I played, the CPU fans suddenly went dead, and anything graphics or CPU heavy did not trigger the fans.

The kernel_task process throttles the CPU, by having it do "nothing" in short intervals.

I googled about this problem and saw that it was usually related to thermal issues with the CPU on Macbook Airs. But iStat Menus, and touching the machine told me, it was cold. Rebooting or looking for troublesome programs solved nothing.

But then I tried unplugging the machine from power and noticed that the battery was almost flat. I had also noticed that the power lamp on the plug was off (what I thought was normal for this type of plug).

After plugging the power back in, it started charging and everything is back to normal. Still, there may be a power management issue with the battery, which is a separate issue.

My guess is that the kernel thought that the power was not plugged in, even though this was indicated in the menu bar and so, did not charge, not even after rebooting. When the battery went flat, the kernel_task process started throttling CPU usage.

I hope this is of help to anyone. :)


macrumors newbie
Jan 5, 2012
Southern California
Identical experience

I stumbled across your post after searching online and browsing through numerous forums. Like you, I found that most discussions regarding the kernal_task CPU overload had to do with MacBook Air and a Thermal CPU issue.

However, that is NOT the case with the MacBook Pro.
Like you, I experienced this CPU overload at relatively low operating temperatures.

To quantify
I'm operating on OSX 10.7.2 LION (11C74)
Processor is the 2.3 GHx Intel Core i5

I even went as far as installing a new hard drive and restoring the operating system to no avail.

Your findings confirmed what I thought was a complete coincidence. My symptoms typically begin as the battery life approaches 65%--CPU will rise to nearly 350% or higher. The moment I attach the magnetic power adapter, the CPU utilization will drop to 1.5%. As soon as I remove the power adapter, the CPU will immediately rise to its previous levels.

At least I know how to remediate it, however, this development severely constricts the portability of the MacBook Pro. Furthermore, the inability to swap fresh batteries into the later generation of laptops from Apple, makes this a show stopper unless one can get to an AC outlet.


macrumors newbie
Jan 5, 2012
Southern California
Update - Fully resolved

to further update:
I was able to fully resolve this issue.
From further searching, I discovered other similar discussions and one suggested the removal of a handful of possibly errant applications or drivers.

I inventoried those applications that had been installed on my Macbook Pro since the symptoms began.

I first removed a Virgin Mobile App for the MC760 USB aircard. This card does not support 64bit anyways so I uninstalled it per manufacturers instructions.
There was a little relief as the CPU utilization dropped about 100points.

So I removed a Garmin Training Center app along with the Garmin communicator which interfaces with a Garmin Edge 305 Bicycle computer that I use for collecting training data.

After a reboot, CPU utilization from the kernel_task has settled down to about 1-2%.

In my case, I can confidently say the problem was caused by an errant application/driver and once removed returned CPU resources back to the operating system. It has since operated normally using Battery and/or AC power for the past 24 hours with no recurrence of the CPU overload.


macrumors newbie
Jan 11, 2012
I'm experiencing a similar problem. Here's the quick specs of my 2011 MacbookPro:
OSX Lion 10.7.2 (11C74)
2.8 GHz Intel Core i7

I was running a video call one night and all of a sudden, I notice that my CPU usage had jumped to over 350%, all due to kernel_task. The temperature of my computer briefly spiked up, but then my computer quickly turned itself off and I rebooted it. This time, it booted up much slower and I still noticed that kernel_task was still at it. I closed any extraneous programs - Steam, Dropbox, etc and scanned the activity monitor numerous times for trouble applications/processes and saw nothing.

When I rebooted my computer again, all the temperatures read to be fairly cool, yet the fans were running at the maximum 6200RPM even though they are set much lower in iStat. I now run the computer in Safe Boot, and the fans are still running at full but kernel_task is acting normally.

Obviously I'm quite frustrated and I've been combing through your suggestions below, but nothing has seemed to solve my problem. What else could it be and do you think I should just haul my laptop into Apple and see what they say?


macrumors newbie
Jul 27, 2014
I believe that kernel task is a catch-all for a lot of problems, but I think that my experience is fairly common, and I couldn't get any info online - everyone was talking about application issues, etc, and none of the solutions helped at all.

I would get kernel_task using all of my cores, and since it's the highest priority process, it would preempt the UI and make the computer completely miserable to use. It would also happen fairly infrequently and in a way I couldn't predict, so it was a pain to figure it out.

First, I disabled all applications with kernel extensions, and turned off most background processes. No joy.

I took it into the Apple store, and we couldn't replicate it, and then it would happen again when I returned home.

Eventually I realized that this happened more when it was warmer in the office, and putting the laptop on a stand with a fan blowing on it would make it less likely to happen, so I realized it was probably a thermal issue.

I opened up the laptop, removed the fans, and saw the problem - the heatsinks were completely matted with a thick solid layer of dust, preventing any airflow from getting through and cooling down the heatsinks. This was causing kernel_task to try to throttle the CPU aggressively, in an effort to keep the CPU from overheating.

It's a fairly quick operation if you have the right screwdrivers, though make sure you ground yourself first. If you feel squeamish about it, just suggest it as a possible solution to the tech at the Apple Store Genius Bar.

Good luck!
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macrumors newbie
Nov 8, 2014
Hi, I had same problem with CPU is on 350%, Fan is working as crazy, I found video on youube that suggests to delete files in system/library/extnesions..... but my MBP is 9,2 and this model is not in that list,- there are just PROs till version 8,3...on the other website I found
soulutions to delete all these files.....

BUT nothing helped, problem is still going on. I have 1é.10 version....Please tall me what to do step by step
I also reinstalled OS X but nothing helped.


macrumors newbie
Nov 8, 2014
Hi, here is whole my story of what happened, please read it and ask me, I really want to resolve his problem but I don't know how!!!!

MacBookPro 9,2 (MID 2012)

1. During summer holiday(OS X 10.9) and watching videos from external disc system crashed and appeared grey desktop with question mark - macbook was in servise and there was changed SATA cable + trackpad. After this everything was perfect. I just noticed little problem with USB external mouse(no APPLE mouse)

2. I upgraded system on OS X 10.10, everything was still perfect.

3. Two weeks ago while I had USB connected to mac and just browsing internet, Fan started to go really loudly and heavy, I opened"activity monitor" and for first time saw kernel_task process, it took 350% CPU useage and 650MB RAM. I turned off mac, waited and everything was fine.

4. This happened few more times. I found topics and solutions should be - reinstaling OS X. So I did. Everything was fine till today

5. It`s 3rd day after reinstalling system, and problem with kernel_task started again. So I started digging on forums.

6. Found few advices about kernel_task and this video:

its good solutions but not for me, in folder where I should delete specific file is not file with my type of macbook (mine is 9, folder the highest is 8,3) creator of video has no solution for my type.

7. so I continued looking for solution and I found this article:

so I did it, it helped, fan started going slower and quieter until everything was good and perfect, safari started working fast as never was.

8. I was so happy, but after 1 hour it started again, it is different now, fan started was fast, loud but it took just 1-2minutes and again is everything good. This happened again 3-4 times.


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