I was getting a cpu fan failure message on start up. Sure enough the cpu fan was not working. I tried another fan to no avail. I bypassed the motherboard with a 3 pin to 4 pin adapter and the fan works like a charm. The problem is the motherboard doesn't know the fan is operating and I am unable to get to the bios to change the setting. What do I do? The board is a Asus A8AE-LE socket 939.
If your board cpu fan port has failed, then you may have a problem if the system wants to shut down since it can't detect the fan. But if it runs with the adapter, then continue using it. Your board is sometimes available on ebay; don't know about pricing.
The motherboard needs to believe that the fan is spinning, if there is nothing connected to the CPU fan header it will give you that error because it believes that there is no fan connected. If your CPU fan header is fried its a good idea to look into a new system or a replacement board.
Basically it is a motherboard issue. Updating the BIOS, replacing the heat sinks and both fans didn't make any difference. It took me 7 months and multiple home visits and hours on the phone before they finally fixed it. If the BIOS update didn't work (I still have R166551 and R215335 on my desktop from their remote logins) INSIST they change the motherboard while it is still under warranty. Tell them it is a known problem and that it has been an ongoing issue in the Dell forum for nearly a year. I cut and pasted the link to the forum for the tech I was on chat with...that seemed to work.
Also, I noticed I get much better service through the chat interface than on the phone...not sure why. Good luck!