My 2005 Prius has a check engine light, and will not start I can hear a clicking noise coming from the trunk of the car. No red triangle of death. And battery reads at 12.1 volts
12.1 with the car off is pretty low. have it tested free at an auto parts store. any idea how old it is?
12.1 volts is plenty to read the trouble codes, which will give you more information about why the car won't start.