I finally diagnose my 2011 Prius III (151k miles) and the code the OBDII scanner generated was P0A94..
Does a warranty enhancement like ZE3 apply where you are? Where it applies, the ZE3 program runs for fifteen years with no mileage limit.
Looks like it does. The dealer called stating the extended unlimited warranty for 15 yrs. Crossing my fingers the service is covered