As far as a dew sensor fault is concerned, "IF" the sensor has been properly cleaned and the warning is still there then no amount of resetting will help anything, (not that this is possible anyway!) as a defective sensor cannot be cured by any means other than by-passing it electrically via a simple modification. In saying that though, anyone attempting the mod "MUST" be familiar in working with small electro-mechanical devices, as fiddly work is involved separating the case / PC boards.