I don't have an outlet fan but I do have an inlet fan. The default lowest rpm threshold setting is 250 rpm. From your thread it could be that you need to take a look at your outlet fan (actually the back fan). Perhaps it needs some maintenance or replacement. It is a warning sign for you to take action.
As I said, this only occurs immediately after waking from sleep mode. There have been no warnings during many hours of normal operation. The meaning of the warning is clear. The question is whether it is valid.
Mine does not give any warning after waking up from sleep mode. During sleep mode the fan completely stop. But when waking up, it accelerates to the normal speed of around 800 rpm as monitored by the Desktop Utilities. I have set it to run at low speed in the bios.
For the benefit of others experiencing fan alerts on wake from sleep, apparently it's a known issue. Intel support acknowledged they have seen this behavior internally. Ideally the Desktop Utilities should not report a false alert due to fans stopping during sleep mode. Intel support agreed, but it's not classified as a bug at this time.
The workaround I used is to uncheck the Chassis Fan sensors under Options -> Active Alerting Options -> Alert Setting. At first I thought there could be an issue with my chassis outlet fan. I only deactivated that one, but on next wake from sleep an alert was displayed for the inlet fan. So, you may have to deactivate alerting for all chassis fans. Setting lower threshold to 0 may work also.
Intel support said they sometimes have to do the same thing internally (deactivate chassis fan alerting). Hopefully, this "quirk" will be resolved someday or at least listed as a known issue in the readme file. Chassis fan monitoring works (does not produce false alerts) in some configurations and the problem does not occur with my processor fan, so there is evidence it can work properly. Again, Desktop Utilities is a great tool, so I'll live with this to get all the other goodies.
Update: Support suggested going to Options tab, select "Set Sensor Threshold" and click on "Fans Redetect" and restarting Windows as a possible fix for fan alerts upon wake from sleep mode. Unfortunately, this did not eliminate false alerts on my system.
I suspect threshold is being checked within milliseconds after waking from sleep--before the fans have a chance to spin up. I decided to experiment a bit and reduced lower sensor threshold from 250 to 150 for input and output chassis fans. And it worked! No more false alerts!
Ideally, RPM threshold would be higher than 150, but it's better than deactivating the sensor. At least alerts will occur if a fan stops. Interestingly, processor fan has not been a problem. In fact, I increased lower threshold on that fan without any false alerts.
Hope this helps others experiencing the sleep/fan alert issue.
Update: Just got an alert that chassis outlet fan slowed or stopped (0 RPM) upon wake from sleep. So, reducing lower threshold does not entirely eliminate false alerts, but it does reduce the frequency.
I am running IDU 3.1 and having similar issues. I have a DX58SO2 with BIOS 1910 and coming out of sleep the CPU and Chassis outlet fan were not on and reporting errors. I set the thresholds to 0RPM and the errors stopped. The CPU fan is on as normal running about 800RM but the Chassis fan is not on at all. If I reboot all the fans work fine. the POST 80h code is 30 which I think is normal when returning from sleep.
Any other ideas on how to fix this? Setting the threshold to 0 is bad since if the fan dies you won't know.