Previous 1 2 Next 17 Replies Latest reply: Oct 18, 2014 1:17 PM by a. katrina15
sebastiendl Level 1 (0 points)



I've noticed that a lot of people have been having trouble with the kernel_task process, but I couldn't quite find a situation similar to mine (most seem temperature related).


Here is the situation (15' MBP, mid-2010):

- on boot (while the apple logo is shown), the fans speed suddenly jumps, and stays there, even if the computer has been off for a while.

- boot takes a little over a minute, which is considerably slower than what I was used to before today

- when finally started-up, the activity monitors shows kernel_task using between 160-180% of the CPU!

- temperatures are shown to be around 30C, except for the mem controller at 40C (still very low temp), but the fan speed is arround 6000rpm for both fans.

- this happened out of nowhere, as I woke the mpb from sleep this morning.


Since then I've tried:

- multiple reboots

- install all updates

- uninstall flash player (some people where having trouble with that)

- empty the system cache with Onyx (reported as a cause of slow boot)

- reset PRAM

- reset SMC

- put some ice packs under the mpb to cool things even further!


And so far, nothing has worked! I've had this laptop for 1 year, and nothing had ever failed. I upgraded to lion a few weeks ago, and everything had been working fine since the upgrade. This really happened out of nowhere, and none of the many forums I have read could offer a solution, and cals to apple support do not seem to yield better results (though I scheduled a call with them at 9am this morning, we'll see).


Has anyone had a similar set of problems?


I appreciate any help or advice you may have!




MacBook Pro, Mac OS X (10.7.1)
  • mactechconsulting Level 4 (2,775 points)

    I had the symptoms you describe. Im my case it was OLD APC software that had my Fans at 5700rpn's and temps at the limit!!


    Open activity monitor and show All Processes, Then see what is using all recources of the OS and Quit the process and see what happens, try to  track down what incompatable software you have installed.


    This worked for me...  I went to APC's site found the legacy sofware Re D/Led it so I could get the Removal script that was included in the install DL pkg!!


    Good luck or clean Install...

  • sebastiendl Level 1 (0 points)

    Thanks for your advice. Unfortunately, I carefully reviewed all the processes running, and the only significant resource drain comes from the 'kernel_task' process (160-180% as I mentionned earlier), nothing else really goes over 1% of cpu usage or a few 10s MB of memory.


    I will probably try a fresh install tonight, but since this happened out of the blue (I closed the computer before going to bed, all was fine, opened it in the morning, and the fans went crazy right away), I'm afraid a fresh install won't really do much.


    Thanks again!

  • mactechconsulting Level 4 (2,775 points)

    As it bears repeating, Spotlight does its thing more often in the beginning after Install, and sometimes even seems to re-index the drive for more reasons..This also produces the behavior you describe, along with Bad intinialize??

  • sebastiendl Level 1 (0 points)

    I just spent over an hour on the phone with Apple, and here is what we found:

    - when starting up in safe mode (hold shift at startup), the kernel_task does not seem to run wild (~1%), however, the fan still runs at full speed.

    - I have just made a fresh install of os x lion on an external drive, started up on it, and the problem remains the same, high fan speeds, kernel_task process at over 160% cpu usage.


    Additionally to what I had already tried we did:

    - repair disk

    - repair disk permissions

    - re-reseted PRAM and SMC

    - removed all login items (except iTunesHelper)


    As for spotlight, I can see the process running in the background, but it uses very little of the resources, so I do not think it is a problem here.


    I am waiting for a call back from Apple now now that I finished the new install, I will post any further development here. Meanwhile, if you or anyone else has anymore suggestions, please let me know!


    Thanks again!

  • sebastiendl Level 1 (0 points)

    UPDATE: still no news from Apple, but I kept looking arround and eventually performed an Apple Hardware Test (hold D on startup, I didn't even know this existed) which found the following error: 4SNS/1/C0000008:TCOD--124. After some googling, it turns out this may be a heat sensor issue, although there is very limited references to that specific error code, and the only resolved case was achieved by turning the MBP off for a few hours (I've already tried that, desperate...). Sounds like I'm going to have to invest in Apple Care!

  • eww Level 9 (52,980 points)

    An Apple Hardware Test error that includes "4SNS" is a sensor error, and in your case I have no doubt it's a temperature sensor. That would account for the strange combination of cool operation and high fan speed, since whenever a temp sensor fails, the fan or fans run at full speed just in case the faulty sensor is failing to report a very high temperature that really exists in the machine. Usually there is no problem of excess heat in reality, but the fan speedup is a safety precaution.


    What remains completely unexplained, at least to my way of thinking, is how your CPU can be getting the extremely heavy use reported by Activity Monitor without its temperature going far higher. I don't see how a faulty sensor can possibly account for that — in fact I can't think of anything that would.

  • sebastiendl Level 1 (0 points)

    The logic also escape my understanding, especially since the heavy cpu usage does not happen in safe mode!


    Finally I heard back from Apple, and they are sending me a box to send the mbp for repairs, for the nice flat rate of $350, just one month after the warranty expired! At least they were very nice and helpful as usual, but this kind of timing is a bit annoying!


    Thank you all for your answers and hepful suggestions. If I have a more detailed report from the hardware replacement I will post it here so that it may help people with similar problems.

  • philbilodeau1991 Level 1 (0 points)

    i have the exact same issue and i was wondering whatexactly  did you say to the apple reps to have this issue resolved. now that i know the issue i just want it dealt with as soon as possible; my warrenty ran out last month as well; thanks;

  • sebastiendl Level 1 (0 points)

    So my computer is back and all fixed. They had to change the logic board and apparently they not only changed but also added some temprature sensors. If you want to get it fixed fast, run the Apple Hardware Test (hold D on start up, and if that does not work, use one of the 2 CDs that came with your laptop, the one that says AHT or Apple Hardware Test on it): this will give you an error message starting with 4SNS (if your problem is the same as mine), and if you just tell that to Apple on the phone, they'll have you send or bring your laptop to be fixed (flat rate ~$350 if you send it).


    Good luck with that!

  • ouzcuq Level 1 (0 points)

    Backup your files before doing anything.


    I had exactly same issue, on my part i've tried:


    1. Apple Hardware Test (No Faults Found)
    2. Format Disk and Fresh install of Snow Leopard.
    3. Resetting Pram.
    4. Resetting SMC
    5. Installing all updates
    6. Repair Disk
    7. Repair Disk Permissions
    8. Verify Disk



    i was thinking to get new logic board. But finally i opened inside the MBP and replaced the thermal paste. It was dry and the screws that holds CPU and Nvidia Card was kind of loose. Then again it was on 2 years old MBP. It has been a week, MBP runs like new no issues so far.( knock on the wood. )


    Hope this helps

  • NickGartner Level 1 (0 points)

    I've had this same problem, CPU going insane, up to 500% usage, with the normal amount of threads, and the fan running full speed even though the temp was 91F or lower.


    Eventually, I opened up the console and looked into what was calling the kernal task. It turned out Adobe Air was throwing a call on behalf of Adobe Story hundreds of times a minute. I uninstalled Story and the problem went away immediately.


    So if you're like me and your hardware test checks out fine, have a look at the console and see if there's anything out of the ordinary.

  • Tristan Summers Level 1 (25 points)

    I have the same issue (2.66 2010 MBP Hi-Res Anti Glare.)

    I took it to Apple Store Covent Garden, JUST within warranty.

    18 days later my machine has a new Main Logic borad, heat sensors, top case, palm rest. etc.

    I turned it on.

    The fans kicked in. All processors at 50%, big ole kernal task.


    I took it back, geniuses rest SMC and tested it under load and it was fine.

    weirdly it failed diagnostics at first but then seemed fine

    I came home. Fans kicked in...


    I took it back. Diagnostics failed heat sensors again

    Replaced logic board and heats sensors again, but more carefully this time just in case, tested again.


    I took it home. FANS FANS FANS.

    Last time I was in the store I was told my machine was fine and had been thoroughly tested.

    In mac store, no fans.


    I erased hard drive and clean installed Lion


    I replaced hard drive with OCZ SSD, clean LION.

    Software update




    Onyx complete clean/maintenace



    switched back to Snow Leopard SSD

    PRAM SMC ONYX etc.




    replaced RAM, memtest-ed. fine, FANS


    gonna try again but up to nearly 2 months of all my spare time trying to shut this thing up so I can sell it.

  • sameerfromwa Level 1 (0 points)

    I have the exact same symptoms as you. Runaway fan, and high kernel CPU consumption unless I login to safe mode. However, fan keeps going.


    I tried everything you tried and it didn't help either. I just did a hardware test (pressing D on startup) and unfortunately, that came back with no issues either.


    I have a clean install of OS X now after I deleted my old install. Looks like I will have to take it to the Apple store.


    I am convinced that it is a hardware issue and I am perplexed by how that can result in the software kernel utilization. Also, I don't understand why the kernel is ok when I login to safe mode but the fan keeps going.


    Seems like some service that is responsible in tying the kernel to respond to the hardware issue is turned off when I login to safe mode. That's the best explanation I can come up with.


    Hope the geniuses at the Apple store can find what's wrong.

  • Tristan Summers Level 1 (25 points)


    In the end it turned out to be a faulty display cable.


    I am not sure how this was tested for, maybe they could power up without the screen?

    So if there is any sort of loose connection, and something seems to be missing, the fans go mad just in case.

    Doesn't explain the CPU thng though.

    Maybe it was a starting back from sleep thing.

    2 months of silence now though so all seems good.

    Apparently this is quite a common fault.

    It's just none of the other geniuses knew that.

    Obviously I don't mind having a new screen, top, logic board, senor, palm rest, side panel etc. but it's weird how long this took to diagnose.


    Anyway.mention possible faulty or badly connected cables and see if it helps



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