2014 Prius c two

do the brake lights come on when you press the brake pedal?

might you be pushing the power button too quickly before pressing the brake fully?

did you tighten the negative to body connection as well?

lastly, dealers don't understand 12 volt batteries. take it to auto zone or other for a free load test and print out, if you don't own a volt meter

 

I suggest turning on the headlights with car off. If they come on, then it's not the 12v battery.

 

A two won't have a power button. Plain old steel shank twist key.

Rodent intrusion? They love to eat wires. Wear and tear on the keyswitch? unusually heavy keychain? Just spitballing.

 

Original battery?

 

I just replaced my original battery on the 28th. 119k miles and 7 years, not too shabby.

 

Have you done (or had done) any testing of the 12 volt battery. In ascending order of effective testing:

1. (assuming your year has the under-hood jump point) Leave the hood ajar overnight (to avoid any "wake up" of the car) and in the morning measure the voltage of the battery with a digital multimeter. The under-hood jump point is fine for this. Post what value you get.

2. Assess the battery with an electronic load tester. There are DIY level versions (Google Solar BA5 or BA9, a couple of the options. Most battery retailers will have a pro-level tester and will test for free. Dealerships also have them, will charge a bit though. With these you hook up directly to the battery posts, input the type of battery, the rated Cold Cranking Amps (stock batteries tend to omit this value. If you can'f find it, try 325, it'll be close), then run the load test. It'll tell you the measured CCA, and give a verdict, if the battery is vaiable and so on.

All that said, considering the age, it'd be a good time to just replace it.