Toyota yaris 2012 not starting

Mate, I need your help with my car. It's a 2012 Toyota Yaris, and last year it wouldn't start, so I changed the Battery. My wife drives it, but she only does like 2,000 miles a year. She just drives it to the grocery store and her mom's house, which are both less than two miles away. So it's only short trips.

But after three months of replacing the Battery, it wouldn't start again. And when I unlocked it with the key, the trunk wouldn't open either. I had to jump-start it, and then it worked. But the next day, the same thing happened, even though I had driven it for half an hour. The next day, I drove it again for 30 minutes, and after that, it worked fine for a few months. But then it happened again. The trunk is locked, and the car won't start. I checked the Battery, and it's fine. But it's losing power when it's turned off, and my neighbor told me that my car lights were flashing while it was locked. I don't know how that's possible.

Now, here's another problem. Sometimes when I'm driving, it'll just lose all power and won't start. But after some jiggling, it starts again. So I have two problems. Sometimes it won't start at all, and sometimes it loses power while I'm driving. The last time it happened, I pressed the accelerator, and it didn't turn off.

My first reaction is a mouse or something has chewed some important wires or there's a corroded earth strap somewhere...

I'd check the Battery and chassis earth. Poor earth connections cause a multitude of issues. Connect s jump lead direct from Battery earth to the engine and also Battery to chassis. Give it a  try.

Topic moved to the Yaris forum

Given the short trips involved you probably need to give it a separate charge, with a mains powered charger, every month or so. It's what I've been doing with my wife's car for a while as she rarely goes far these days.

I have a voltmeter in the aux socket and when the ignition 'on but not started' volts gets down to 12V or less I stick the charger on which gets it back to 12.5 or so. 

Rinse and repeat.

sound like a bad earth,  disconnect the Battery clean the terminals and Battery post with wire wool or scotchbrite (green kitchen scouring pad will do)

How old is the Battery ?

If this model has an alternator, check that the earth braid isn't broken.

Check the Battery voltage when the engine is running, it should be between

13 and 14 volts