MacBook Pro suddenly started spinning fans at 100% while lid was closed for a couple of hours

macbook prosleep-waketemperature

I've been noticing some issues with my MacBook for a while now. Firstly, kernel_task sometimes takes over extreme amounts of CPU and the whole computer starts acting slow even when I'm not using it for any heavy tasks.

Note that this is a 15" MBPro 2015, all specs maxed out.

Fans are also often at full speed for seemingly no reason (just browsing the net) but that has been going on forever since I bought it, and I heard that is relatively normal for those MBPros.

But last night the weirdest thing happened. I closed the lid and went to sleep. Several hours later in the morning, I was awoken to my MacBook fans going on at 100%.

I got up to check it out and the bottom plate was pretty hot and fans still going at 100%. I opened the lid and I couldn't get it to turn on. The screen would not show anything no matter how long I waited and how many keys I pressed.

I ended up force shutting it down (holding down the power button).

Any idea what could be causing this? Is there any way I can try to figure out the problem, or is taking it to Apple for repair the only option?

Best Answer

The first thing I'd do is a NVRAM and SMC reset (in that order). Before following the steps below, ensure you have no external hardware connected and that you're using the built-in keyboard.

Reset the NVRAM

Reset the NVRAM on your MBP as follows:

  1. Shut down your machine. Yes, a full shut down, not just logging out.
  2. Press the power button and then press the commandoptionpr keys. You have to make sure you press these keys before the gray screen appears or it won’t work.
  3. Hold those keys down until your MBP reboots again and you here the startup chime.
  4. Let go of the keys and let your MBP reboot normally.

Note: When you log back in you may need to readjust some of your system preferences (e.g. speaker volume, screen resolution, startup disk selection, time zone information, etc).

Reset the SMC

There's a couple of ways you can reset the SMC on your MBP, however I prefer the following steps:

  1. Shut down your MBP
  2. Keep the power cable plugged in
  3. Press at the same time shiftoptioncontrol (on the left side of the keyboard) and the power button
  4. Let go
  5. Turn your computer back on with the power button

After resetting both the NVRAM and SMC, use your computer to determine if the issues still persist.

If you're still having problems, the it's time to test your hardware with Apple Diagnostics.

Run Apple Diagnostics

Follow the steps below to run Apple Diagnostics:

  1. Fully shut down your Mac
  2. Restart your Mac
  3. Immediately press the D key and keep it down until you see the Diagnostics screen appear
  4. Wait for Diagnostics to finish (this typically only takes a few minutes)
  5. Once complete, one of two things will appear on the screen:
    • a No issues found message
    • a brief description of any errors found plus further instructions
  6. If the diagnostics test does find errors, take a note of what they are

Note: If pressing and holding the D key at Step 3 doesn't work, start again at Step 1 and, at Step 3 press and hold both the OptionD keys instead. This will try and run diagnostics from the internet instead, so you will need to allow more time for it to complete.

Regardless, take a note of what happens and let me know how you went.

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