Alarm going off for no reason

HI All

My Corolla Hybrid 2l sport  today started sounding the alarm while standing on my drive.

I managed to get to the car pretty quick but could not see any attempts at theft or cat disconnection.

Now i know that this car has no tilt sensor etc so i am puzzled why the alarm went off. I addition there were no signs of forced entry through 

the doors and all windows were intact. I was wondering what physical action would trigger the alarm.

Might have a vibration detection type of alarm sensor. Been pretty windy recently, so maybe that has triggered it. A neighbour of mine has one of those alarms and it's always going off when the wind picks up 🤬

Very often when a car alarm goes off without obvious reason likely been triggered by an insect or small animal locked inside, when it moves the sonar sensors detects it and set the alarm off, can happen also when windows left partly open for airing the interior and some wind blows a leaf from the outside in, the sensors react again and alarm goes off. Perhaps something like that has happened to you. There is a button to turn that function off and so you can leave a passenger, a pet or windows half open and lock the car without worrying about the alarm. This button should be located near the front interior lights switch on the roof lining. 👍

This happened to me, I turned the ultrasonics off overnight, then back on in the evening to see if it had got better. One evening  I saw a moth trying to reach the nearby street light. I let it out & didn't have the problem again. It took 3 evenings before I saw the moth. 

Good luck

Hi all thanks for the responses.

Its a bit of a mystery but Tony mentions this strange  Off button located on the roof of which there is no mention of in the manual but throws some light on its possible use. The puzzle here is   how do you operate it ? and when do you know its on or off  ? is a  question i see from other members contributing to this forum are having considerable trouble getting answers to. Now some suggest lock the car but leave the drivers side window open and stick your hand inside and wave it about. Now this is a technique i do not favour as i want to stay on good terms with my immediate neighbours. Any other suggestions gratefully received.

https://www.toyotaownersclub.com/forums/topic/193730-alarm-system-on-2019-corolla-hybrid/

This might help

31 minutes ago, Louie said:

Hi all thanks for the responses.

Its a bit of a mystery but Tony mentions this strange  Off button located on the roof of which there is no mention of in the manual but throws some light on its possible use. The puzzle here is   how do you operate it ? and when do you know its on or off  ? is a  question i see from other members contributing to this forum are having considerable trouble getting answers to. Now some suggest lock the car but leave the drivers side window open and stick your hand inside and wave it about. Now this is a technique i do not favour as i want to stay on good terms with my immediate neighbours. Any other suggestions gratefully received.

The button is documented on p.104 of the full (online) manual. I'm away from the car at the moment so I haven't tested this but the manual says that:

(1) The intrusion sensor (interior motion detector) is on unless you deliberately turn it off by pressing the button before leaving the car and locking it. It doesn't stay off next time you lock the car unless you set it off again. If you turn it off, you can change your mind by pressing the button again so don't press the button twice just to make sure! 

(2) Each time you press the button to set or unset the motion detector a message will be displayed on the multi-information display. No need to upset the neighbours by testing it!

I just checked and there’s a clear message each time you press the button. Great if you know about it. Problem is that if you’re looking up at the button you’ll never notice it!

I tried to ring the dealer on this problem today but was put on the death hold ☠️. Anyway thanks  to Geoff i am a bit wiser now.

Did you managed to get this fixed?

Mine has started doing this randomly in the evenings, sometimes when a car goes past and sometimes not. Doesn't happen during the day.  The car is parked where it's always been and I've been to check around the car and inside but so far nothing.

The only thing I can think is that the car is used occasionally and I don't always get to do the hour weekly charge recommended by Toyota so I wonder if the Battery is low voltage but the car never struggles to start...

It's booked in for the dealer to investigate next weekend.

Maybe miles off the mark here but do these systems have an under bonnet switch to detect the bonnet being opened? That was a problem with the old Corolla (T Sport) and the alarm going off seemingly randomly. All it needed was either the switch bracket repositioning by just a millimetre or two (the proper way to fix it) or sticking a very thin piece of something where the switch plunger touches the bonnet to make sure it depresses fully. Even the bonnet contracting and moving as the engine cooled was enough to set it off. 

Of course the latest models may not have anything like that...

14 minutes ago, Mooly said:

Maybe miles off the mark here but do these systems have an under bonnet switch to detect the bonnet being opened? That was a problem with the old Corolla (T Sport) and the alarm going off seemingly randomly. All it needed was either the switch bracket repositioning by just a millimetre or two (the proper way to fix it) or sticking a very thin piece of something where the switch plunger touches the bonnet to make sure it depresses fully. Even the bonnet contracting and moving as the engine cooled was enough to set it off. 

Of course the latest models may not have anything like that...

  

Good read, this makes me thinking if one of the doors hasn’t been properly shut and the car managed to lock and set the alarm then after the door had released  a bit tension and the button jump out so the car alarm detects a door opening and sets the alarm off? Just as possible theory. 🙂👍

Well just for fun i went out to the car last night and did the following:

• Had the car "on/ready" for nearly 30mins
• Checked the tyre pressures and pumped them up, they were a couple of PSI down each tyre so maybe that was causing the car to wobble?!
• Opened all the windows and took out a duster and wafted it around all the interior (neighbours probably thought i was insane)
• then closed the windows and fumigated the car with fly spray

It's just weird how it only happens at dusk/night and either it will happen when a car goes past or it will happen when nothing goes past.  I'm parked on a main road in and out the village.

@Mooly i've checked all doors and windows and all are 100% shut/closed now

@TonyHSD hopefully the dealer will be able to check that if the Corolla has it.  I do wonder if there is some sort of alarm diagnostics a bit like commercial building alarms that say what sensor was triggered? Maybe @Devon Aygoknows?

2 hours ago, bewA said:

i've checked all doors and windows and all are 100% shut/closed now

But is there a bonnet switch? On the old Corolla it was a big plunger type switch located at the back edge of the bonnet. Try gently just applying a little upward  pressure to see if you can set the alarm off. Try the front and rear bonnet edges.

(My Auris has a microswitch wired to the bonnet release catch at the front, something I have never found any reference to as to what it is used for)  

To follow this up.

after converting the car into an insect killbox after fly spraying the interior and leaving overnight an insect of a size enough to probably trigger the interior alarm has met it's maker.

I've had no more issues.

My opinion is that if it was a bonnet switch (not that i've looked for one) it should be triggered when cars etc drive passed my car as the draft of the cars will cause the car to wobble and thus cause the switch to be triggered.  My issue was sometimes it was triggered by cars sometimes it wasn't.

I'm guessing it was all down to an insect (RIP) that was occasionally woken up by passing cars!

My Toyota was repaired following an accident earlier this year. The intruder alarm never went off randomly before the accident but now it does, nearly always after dark. The main dealer has looked at it but found nothing wrong. But thanks to @Mooly I think the bonnet (which was included in the repairs) might be the culprit.

I own a Toyota Etios 2021 model. In the winter especially the alarm goes off during the evenings. Sometime 3-4 times a night. Why does this occur? I have checked: all windows are closed, no bugs, Battery is perfect. This is quite  embarrassing as I often stay at guesthouses for work. I have at times had to leave the door to the vehicle open without the alarm being activated to prevent this. What can be done? 

I would go with as mentioned in my previous post from last year that you invest in a can of fly/bug spray and spray it in the car and leave it for a few hours, if it still happens then my suggestion would be to take it to a local dealer to investigate the car.

The other thing to try is exercising the various door switches to check they are all working correctly, operate them each a few dozen times to get the contacts and mechanism working.

Some alarms ( don't know about Toyota)  can go off if your air vents are open and go off caused by a gust of wind , even electrical interference,  9 times out out of 10 it's the internal sensors .

My RAV/4 2019 seems to go off about 10:30 each night. I once owned a Ford Scorpio that the alarm would go off regularly at 7am in the morning. I discovered long after that it was caused by the radio switching on in the background to collect traffic reports so that when I got into the car for my commute I wouldn't have to wait for live reports. The act of switching the radio on increased the current by a few milliamps and this was detected by the car's alarm system, designed to detect when doors were opened etc. As the RAV/4 is connected to the Internet I wondered if maybe Toyota were downloading data at night and causing a slight increase in current drain which was then detected by the alarm system? Any thoughts?

Just had the alarm sounding on my Corolla.  Only goes off at night and the only thing recently done to the car was a service and aircon service.  I wondered if it could be the bonnet or doors so have tried to check those.  In the meantime, turning off the interior sensor seems to stop the problem, at least for now.  If it comes back I'll investigate the Battery as it was run flat when the car was not used for 6 months.  

My son now tells me that he saw a moth in the car last time he was in it.  Just to point out how sensitive the interior sensor is.  

I have the sun (moon) roof and use it most journeys and depending on conditions often switch off the interior sensor when parking. Some times there are flies everywhere and just one in the car is enough the trigger the alarm.