When you have a fan plugged into that location, do you actually see it spinning? If the fan spins at all, it could just be the speed sensor...
If it shows an error no matter what fan you plug in there, it's probably a mainboard problem and the only fix could be to replace it. You might shut off and remove power from the system and then take a close look at the socket the fan plugs in to. Make sure it's clean, no dirt or other crud in there that could keep a pin from making contact. Look for any bent wires or anything else strange. Compare with a working fan socket to get an idea of what it should look like. You could even take a little alcohol on a cotton swap and gently clean the contacts in there.
Depending on how clean or dirty your server room is, you have all that air passing right through the fans and those fan sockets are actually a pretty good place to trap stuff. If you removed and re-inserted a fan, it could have jammed some dust or debris in there.
As long as the fan itself is spinning, it's probably safe to keep using the system because your cooling won't be affected, but it may run that fan at full speed. I don't know for sure what the G6 models do in a situation like that.
If it shows an error no matter what fan you plug in there, it's probably a mainboard problem and the only fix could be to replace it. You might shut off and remove power from the system and then take a close look at the socket the fan plugs in to. Make sure it's clean, no dirt or other crud in there that could keep a pin from making contact. Look for any bent wires or anything else strange. Compare with a working fan socket to get an idea of what it should look like. You could even take a little alcohol on a cotton swap and gently clean the contacts in there.
Depending on how clean or dirty your server room is, you have all that air passing right through the fans and those fan sockets are actually a pretty good place to trap stuff. If you removed and re-inserted a fan, it could have jammed some dust or debris in there.
As long as the fan itself is spinning, it's probably safe to keep using the system because your cooling won't be affected, but it may run that fan at full speed. I don't know for sure what the G6 models do in a situation like that.