Question CPU fan speed error detected

emitfudd

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Apr 9, 2017
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Twice in the past week I have turned on my PC and I get a message that says:

CPU fan speed error detected.
Ensure that the CPU fan is properly installed on the CPU_FAN header or adjust/disable the fan speed low limit option in the UEFI BIOS.

After it did this the first time I manually set my CPU fan to 100% and I could hear it spinning. I can also see it spinning through my case window. I also checked AI Suite to see if it showed the RPM's of the CPU fan. It was at the normal 500 to 600 RPM's. Setting it at 100% it runs at about 1500 RPM's. AI Suite and BIOS show CPU temp at 26 to 27C so there is no overheating.

A few weeks ago AI suite was not loading and by my research a Microsoft update borked AI Suite. It is loading now and all my settings look the same as I had them but I am suspicious that this might be the issue.

I also have a code 41 on my motherboard.

Maybe a bad sensor?

7700K delidded but set back to stock speeds since this is now my backup PC
Asus Maximus IX Code
960 EVO 500GB x2
Corsair CMU32GX4M4C 3200C16R. This is 3200 but running at 3000. 4x8GB
GTX 750 TI
Be Quiet Dark Rock Slim
Seasonic Prime Titanium 850W PSU
Lian Li Lancool II Mesh
 
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DaronMal

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Sep 14, 2013
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Do you have anything plugged into the CPU_FAN header? That's the issue. If you believe you don't actually need it due to your setup and you've purposefully not used that header, there should be an option in the BIOS to disable that CPU_FAN header sensor so you can boot normally.
 

emitfudd

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Do you have anything plugged into the CPU_FAN header? That's the issue. If you believe you don't actually need it due to your setup and you've purposefully not used that header, there should be an option in the BIOS to disable that CPU_FAN header sensor so you can boot normally.
I don't follow you. I have used that header for my CPU fan. You're saying having the fan plugged in to that header is the issue? And I'm sure I do need it in my setup because that is the most logical place to plug in the CPU fan. Also I can boot normally after hitting F1 to go into setup. I just exit the BIOS and the PC starts up normally.
 

DaronMal

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I don't follow you. I have used that header for my CPU fan. You're saying having the fan plugged in to that header is the issue? And I'm sure I do need it in my setup because that is the most logical place to plug in the CPU fan. Also I can boot normally after hitting F1 to go into setup. I just exit the BIOS and the PC starts up normally.
Yes, the CPU_FAN header is used to cool the CPU, so the BIOS (as far as I know ALL BIOS do this) will freak out if there's nothing plugged into that header, but either disabling the header in the BIOS or just going to BIOS and going into Windows from there are workarounds.
 

emitfudd

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How old is the cpu cooler?
May be it needs fan replacement.
It's only 6 months old. The rest of the components including motherboard are from 2017. I took the parts from that original build and put them into a new case as my backup PC when I built my new gaming rig in the end of 2021. I assume the sensor is in the motherboard so maybe that is the issue. This setup was used heavily for gaming for over 4 years.
 

emitfudd

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After uninstalling AI Suite 3 this hasn't happened for over a week now.

Edit: Sure enough I turned on the PC this morning and the error is back. Does nobody have any suggestions here?
 
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