HELP! My gas gauge is suddenly demon possessed!

hello, i had the same issue on my 2006 prius, it is just the sending unit, it is located in the tank with the electric pump assembly.
i have already fixed it myself, it is not easy, and maybe dangerous, because of the presence of gas vapors.
do not inted to do it if you are not a mechanic with good tools and knowledge.
you don't need to charge or change battery, or recalibrate anything, no level calibration. it just work after changing it.
you will find explanations and pics here, at prius touring club it is a french website, teeling about prius and more (use a translator if needed).
prius-touring-club vbf/showthread.php?t=6345

 

i have just discovered that fuel tanks maybe different from the european models, i found it on this thread (prius chat) :
the gas bladder: exposed!
i am very surprised that you need to change the hole tank if the fuel pump or the sending unit (gauge) doesn't work !
the sending unit costs only 80.