Prius unlocks itself

Yes it will unlock itself if a second key is left in the car.

 

Odds are that the second key fob is somewhere in the car.

 

If there's a key inside the car, the car should never lock. It'll unlock itself within a second of you pushing lock

You can test this by rolling down your window and leave your key in the seat. Try to lock the car when you're standing outside, it won't lock

 

Has there ever been a situation where water has gotten through an open window on the driver's side? I'm wondering only because mine started randomly unlocking itself too. This started right after it was parked in the driveway with the windows down when it started to rain. It has nothing to do with a fob in the car, a stuck button on the fob, etc, etc. It does, however, only happen when a fob is within about 10 feet of the car after pushing the locking button on the door. The frequency is gradually decreasing, but it still happens about once every other week.

 

Yes I discovered that key fob has to be outside the car to lock vehicle. I also found out if I exit car (in garage), when I have key fob on me after 5 min the car LOCKS! If i want it to stay unlocked I have use fob to unlock from outside vehicle, there has to be some sort on configurable control scheme for locking selection, havent found it yet though. Go figure.

 

My Gen 1 started unlocking itself when one of the lock actuators grew weak, and wasn't able to completely lock the door,

I would get out, push the fob lock button, the car would try to lock, but the position switch in the actuator would be telling the body ECU that it never quite got all the way to locked, and after a few seconds the ECU would unlock everything, presumably as a signal to me that something needed to be looked at.

Making things more complicated, I bought a replacement actuator on eBay ($17 instead of ten or so times that at the dealer), actually three of them before I was done, and two out of three of those arrived with internal switches missing (actually missing, I cracked one of these knockoffs open and the parts were not even there), so the system never quite worked right with those replacements either (alarm would go off if you opened the door with the key!).

Once I got a working actuator in there that had all of its parts inside, the problem was fixed.

 

Thanks for pointing at a possible problem source and solution. Maybe mine isn't related to something getting wet.

For someone who is not a mechanic, is there some way of testing that actuator? Where is it? How tough is it to replace? Where did you finally wind up purchasing a replacement that actually had all the parts in it?

 

In my case, it was the driver's door actuator (stands to reason, it gets the most use). I was able to walk around to the passenger side and look in the window and watch the lock button on the driver's door, while pressing the lock button on the fob. I could see the knob on the door move partway to locked, as if saying "I got it ... I got it ... I got it ... I ain't got it" and all the rest of the doors unlocked again.

Oddly enough, one of the three actuators I ordered on ebay did turn out to be complete.

I had a colleague suggest an explanation to me one time—I have no firsthand knowledge if it's correct—about how these knockoff parts get made and turn up on eBay for a tenth the price through the dealer. It seems some things might be made in the same offshore factory that gets a contract to make a certain part for a manufacturer. They have the design, the molds, and all, and they can just do other production runs where they spend way less on inspection and quality control and materials sourcing than they have to when producing for the OEM, and those are the parts that then go on eBay for $17. Some of them have all the parts and some don't.

It seems like often enough they can get away with it ... as in the case of the lock actuator: it did contain the motor and it did make the door unlock and lock. That's the thing you would obviously test, and you'd send it back if it didn't. But it might be a long time before you have a reason to unlock your door with the key, and wonder why the alarm goes off, and you might not even connect that to the lock actuator you changed months ago, and just assume something else about your car has gone flaky.