My '93 E32 has developed a quirk in which the wiper fluid sensor seems to be claiming that the tank is empty nearly every trip. Of course, it's quite full, so the error is either the sensor or the sending unit. When starting the car, the sensor reads correctly, but somewhere along the drive, it usually warns and then the message is left up on the dash display until the end of the drive. I can't quite associate the misreading event with a particular action, such as braking, downhill, etc, but I figure it's related to something like that.

It's annoying but seemingly of little consequence. Is this something that's easy to fix, or is it one of those things that means replacing some $500 computer?