This error may be related to hardware or software so the fixes may differ for each user.
Dust and debris slowed down the fan RPM.CPU fan isn’t connected with the motherboard cpu_fan header properly.The most common reason that triggers this error is. If the fans don’t spin properly then it may cause an increase in CPU temperature, resultantly it can damage internal hardware. This error shows that the motherboard safeguard feature is working fine.
What Causes ASUS CPU Fan Errors on Startup?