|If you are getting a fan error message it is because the IBM motherboard detect fan speeds from the sensor line. If the motherboard fails to see the RPM's it will halt boot and prevent the system startup.|
You will need a new fan to correct the problem. I have seen this problem on numerous IBM/Lenovo models.
This is not related to dust unless the fan has something preventing it from spinning.
I have also had these fans failing due to bearing failure and not turning.