I have a 2019 MacBook Pro 16" i9 with 16 Gb and BenQ 32" 4K monitor. I am using a USB-C cable to connect this monitor.

At starting it was working fine but after a few months (during those days macOS was updated from time to time), it became impossible to use both screens. The kernel task is getting 1000+ and the MacBook is getting hung, I can not even move the mouse cursor properly. Then I have to shut down my MacBook via the power button.

Then, after I try to use the external monitor directly (the laptop lid will be closed) but still some times kernel task gets 1000+ and I can not work, then I have to restart MacBook again and again.

I am not using any heavy software, just a browser, Visual Studio Code, and PHP/MySQL/Apache.

It feels like I am using a 15-year-old machine.

I cleared the cache, rested the SMC, and reinstalled the OS. I'm tired of using the charging cable and monitor cable on different sides but still, I am getting this issue. I contacted support but still no solution.

Submitted a bug report to Apple but no response.

I bought an external monitor so I can work on 2 screens but I cannot, I have to use a MacBook screen or external monitor only. can not use both at a time and even when I am using an external monitor only then still many times have kernel task high issues and MacBook got too slow and it's impossible to work and have to restart the machine.

Sometimes, it also overheats when the kernel task is high (after the kernel task is high not before).

How can I fix this issue so I can use both screens?

  • "Sometimes, it also overheats" … that's why kernel_task is running so high, it's trying to cool the Mac down.
    – Tetsujin
    Jun 13, 2023 at 11:58
  • @Tetsujin No. it overheats when kernel_task is high and i leave system as it it so kernel_task goes down. within few mins after starting macbook and connecting monitor , kernel_task getting high and i can not work. Jun 13, 2023 at 12:09
  • Have you checked the airways are clear? Do you have a cooling pad? Is the ambient temperature high? If kernel_task can't ramp up the fans high enough to prevent overheating, then it will use all resources to try.
    – Tetsujin
    Jun 13, 2023 at 12:10
  • I cleared it every time. about temperature, I am using air conditioner. but same issue was during winter. i do not have any temperature issue. Jun 13, 2023 at 12:13
  • 1
    Kernel_task spikes in response to high CPU temp; it doesn’t cause it. See this potential dupe: apple.stackexchange.com/q/441348/119271
    – Allan
    Jun 13, 2023 at 13:26

1 Answer 1


It was due to dust at fans. I went to a local shop and ask to just open back cover and remove dust (do not open any part for deep cleaning) and now it's working properly for the last two days.

show whenever we connect external monitor fan could not cool down CPU and kernel task is getting high and system hangs. I am monitoring the temp using this command

sudo powermetrics --samplers smc |grep -i "CPU die temperature"

I will test for the next 2-3 weeks and keep update here.

Update after Few days

so it's working as expected, not issue at all. if anyone facing same issue then try to just clean dust from fans.

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