Alarm sounds whenever car is unlocked.

You've probably noticed the red button on the fob, which is the panic switch. You don't want to depress that switch unless you want the horn to sound.

Assuming that you are not deliberately depressing that red button as you approach the car, you'll need to figure out what is causing an inadvertent activation of that button.

Where is the fob located, as you are approaching the car? If in a pocket, is there something else in the pocket that might apply pressure on the red button?

 

Sounds like a visit to your local Toyota dealer is in order, if you can reliably demonstrate the problem to the service writer.

 

There are several things you could try to narrow down the possibilities. The first is to disable the proximity function of the keyfob by pressing the switch under the steering wheel. You can still use the keyfob buttons, but just touching the door handle will not trigger anything. You'll also have to put the keyfob in the slot in the dash to start the car.

Perhaps the Alarm button on the keyfob is stuck. If you have a second keyfob (I sure hope so!), you could switch to it and see if the behavior remains the same.

 

It sounds like the keyfobs are not the problem. Something in the computers that manage the locking and alarm systems is malfunctioning.

The 30 second observation is particularly interesting. As an experiment, I walked up to my car and touched the door handle. The door unlocked, as expected. I didn't open the door, but instead backed 10 feet away. 30 seconds after the door unlocked, the door locked again without any input from me.

This is a problem for a mechanic with a professional scantool. As a minimum, the alarm can probably be silenced. The Techstream scantool has a parameter at [Body, Customize, Security] called "Warning by Horn" that could be disabled. Another parameter called "Warning by Glass Sen" should be OFF unless there actually is a glass breakage sensor installed (that works...).

 

did you ever get a result? my prius has the same problem now...

 

Anyone figure this out? I also have this problem, and it is beyond frustrating...

 

sounds like wiring problems, mice?

 

Ok, you're both talking about Gen 2 Prii, so the details won't be identical to my Gen 1, but your symptom is just like what I saw after replacing my lock actuator with a defective aftermarket one.

In my car, the actuator has two switches built in: one to tell the computer whether the lock is locked or unlocked, and one to tell the computer whether you are actually twisting the key to lock or unlock it. If the computer sees the door state go to "open" without having seen one of those things happen as a reason for it to be unlocked, the alarm goes off.

If no one has put in a new actuator lately in your car, then the explanation won't be the same, but I would probably still start with those lock actuator sensing circuits first, and look for a bad connection somewhere (probably most likely), damaged wire (less likely) etc.

You really can get all the information you would need out of the service manual and wiring diagram, and yes, you might get some useful information by checking for codes in the body computer. In a Gen 2, I don't know if a scantool is an absolute necessity for that; in Gen 1, the computer can also tell you codes by blinking the 'door' light on the dash. (And if it can't communicate with the instrument cluster to blink the door light, it flashes the dome light instead.

-Chap

 

Thanks for the info - I'm thinking it is something with the actuator sensor as well. This is beyond my fix-it-yourself capabilities, so I'm taking it into Toyota on Friday and will have them check into this. Will report back-

 

thank you, that's more than i can say for your predecessor.