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IS300H - Alarm going off


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I have a 2014 IS300H and the Alarm has started to go off recently for no apparent reason. I've had the car for about 4 years with no issues to date.

It has only happened about 4 times and all of these in the last month. Typically, it happens about an hour after parking up and this after using the car for anywhere from 30 minutes to 2.5 hours.

As an interim measure, can the alarm be disabled (handbook only talks about disabling intrusion sensors - e.g. if leaving a dog in car)?

Could this be a 12V Battery issue? The car is on its original Battery but this has shown no problems to date and the car has generally seen at least an hour of use weekly - despite Covid.

 

Appreciate any help - it woke me at 4:30 this morning and I've been awake since searching for answers. 😮

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Most probably the 12v Battery. By the time the winter weather comes, at 7or8 years old It's bound to leave you stranded anyway. So, whilst you're still mobile, get one fitted at a Toyota or Lexus dealer. There have been instances of radio problems after a new Battery has been fitted, so let them do it , rather than anyone else. If you still have alarm problems, at least you will have eliminated the main culprit.

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If you have a volt/multi meter then measure the voltage of the 12v Battery before putting the vehicle in Ready mode - the voltage has to be quite low for the alarm to trigger.

It may very well be a spider, insect or a 🐍  🙂. Just turning off the interior sensor is the best way to determine if it is interior movement, which is the most common cause for false alarms, or something more serious such as a sensor or Battery issue.

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Thanks for the replies.

My scenario is that if I put the alarm back on, say, an hour after activation, it doesn't go off again. I think this means that if it was the Battery voltage triggering the alarm, it would be some sort of temporary voltage instability. If that's even a thing? As mentioned, I've had no issues whatsoever with the 12V Battery to date - and I've read lots of threads on here of people who have so I know this is thing. The manual does say this about how the Battery can trigger the alarm:

image.thumb.png.bfa8c8ccbeef01feee7e8994a25e25f4.png

If I lock the car with the mechanical key (never done this before), will that leave the alarm off?

I have a multimeter and will check the voltage from the boot Battery terminals later today. If I don't come back on this thread, it means it was actually a 🐍 😲 ...

 

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Answering one of my own questions above - just saw this on page 550 of the manual:

image.thumb.png.c9a527711b820eca6907fa2f1b1b1ff9.png

And while I'm here - Page 99 states how to disable the intrusion and tilt sensor:

image.thumb.png.51d1091b1304b1cf272c710d565ea84a.png

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4 minutes ago, route66 said:

Answering one of my own questions above - just saw this on page 550 of the manual:

image.thumb.png.c9a527711b820eca6907fa2f1b1b1ff9.png

 

You are a star !

You have unlocked one of Nature`s most secure secrets and you have been awarded 50 fictional points.👍👍

If only we had more Members like you !

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On 7/16/2021 at 8:50 AM, ColinBarber said:

It may very well be a spider, insect or a 🐍  🙂. Just turning off the interior sensor is the best way to determine if it is interior movement, which is the most common cause for false alarms,

My alarm has gone off a few times over the years. Same car as yours. It's always been an insect in the car.

My solution has always been to turn off the movement sensor for a day or two until the insect escapes or dies.

I particularly liked the story another contributor described on a similar thread. His alarm would go off at 1.30am each night to his great annoyance. Couldn't find the solution. Eventually his wife cracked it.

Around 1.30 am each morning a fox strolled down the pavement outside the house. The next door neighbour had movement sensor floodlights and the fox passing by turned on the floodlights. The bright light made a moth in the car think it was daytime and it started fluttering about. The car thought there was an intruder and set off the alarm.

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1 minute ago, Thackeray said:

My alarm has gone off a few times over the years. Same car as yours. It's always been an insect in the car.

My solution has always been to turn off the movement sensor for a day or two until the insect escapes or dies.

I particularly liked the story another contributor described on a similar thread. His alarm would go off at 1.30am each night to his great annoyance. Couldn't find the solution. Eventually his wife cracked it.

Around 1.30 am each morning a fox strolled down the pavement outside the house. The next door neighbour had movement sensor floodlights and the fox passing by turned on the floodlights. The bright light made a moth in the car think it was daytime and it started fluttering about. The car thought there was an intruder and set off the alarm.

Cracking story! Amazing they found it out.

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It's reading 12.27V:

image.png

... which according to this diagram posted in the is300h battery problems thread:

image.thumb.png.07b7ef60afe1806a3fc5d7c2ad854b60.png

... means my Battery is ok (or at least ok'ish).

I had a quick look around the car opened all the doors, boot and bonnet but didn't see any insects - or snakes!

Because this has only recently started to happen - and then very intermittently - I guess I'll have to do some experimenting but I might have to wait for a month before I can conclude anything.

Unless anyone thinks it could be the Battery or some sort of voltage instability ...

 

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8 hours ago, route66 said:

Unless anyone thinks it could be the battery or some sort of voltage instability ...

Nope I really don't think so, and whilst your voltage is a little low it would need to be down < 11v to trigger the alarm voltage sensor, at which point you would struggle to power up the vehicle again so I'd rule out the Battery for now.

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All this info here, is why I became a member of LOC UK.

I only purchased my car on Thursday 15th July 2021 (For those reading old posts) 2013 F-Sport with almost 36,000 miles on it

First day my Alarm went off a 23:00, next day, nothing, day after 23:00 awaiting what happens this evening. Was thinking a cat may trigger it but as I have CCTV around my house, I have not actually seen one in the area at that time. 

A quick voltage check on the Battery puts it in the green zone but that was after a run so I will check it again in the morning.

I'll keep you in the loop if I  find anything

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Bought my IS300h in Dec last year and not had any problems until a couple of weeks ago when the alarm went off for no reason.

Happened twice first during the day when just the alarm sounded then the following night when alarm, lights and horn sounded. Took car to Lexus Leeds and after checking it over have arranged to replace the alarm this Thursday under warranty. Not sure if it's part of or all of the alarm they are replacing but will report back.

 

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16 hours ago, Joe43 said:

Happened twice first during the day when just the alarm sounded then the following night when alarm, lights and horn sounded.

 

I didn't know there was a separate Alarm sound. Mine sounds the horn and flashes the lights - the indicators at least, not sure about the headlights

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Quick update.

Today Lexus Leeds replaced internal intrusion sensor,  collected car this morning brought it back mid afternoon fully valeted with new sensor. Very impressed with their service.

 

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  • 2 weeks later...

I'm still working on a solution.

Checked the Battery after vehicle has sat for several hours. Still reading ok @ 12.3 v

Issue has primarily showing in the evenings, first off all at 11pm every other evening, then at 10pm every other evening. Only the over, up until last night, when it went off twice, whilst at work.

tonight I will disable intrusion sensors and see what happens

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  • 3 weeks later...
On 8/1/2021 at 5:29 PM, Kiefels said:

I'm still working on a solution.

Checked the battery after vehicle has sat for several hours. Still reading ok @ 12.3 v

Issue has primarily showing in the evenings, first off all at 11pm every other evening, then at 10pm every other evening. Only the over, up until last night, when it went off twice, whilst at work.

tonight I will disable intrusion sensors and see what happens

***UPDATE***

 

I disabled the interior sensors for 3 whole days and nights, then allowed them to activate after that. 

So, far, no false alerts and waking of neighbours. Been over 2 weeks now.

This leads me to two conclusions:

1. There was some critter, moving around in the vehicle and setting it off. It died or left the building.

2. Disabling the interior sensors removed a glitch in the sensor system.

 

Unable to conclusively disprove either of those, so, as Toyah Wilcox would say..

It'th a mythtery! 

Apologies to those not akin to the reference or are offended by humour.

 

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10 minutes ago, Kiefels said:

 

 

Unable to conclusively disprove either of those, so, as Toyah Wilcox would say..

It'th a mythtery! 

Apologies to those not akin to the reference or are offended by humour.

 

If as you say it could have been a critter, should you have said "it'th a mothtery"?

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As the OP, I felt duty-bound to post an update to this thread but shied away - didn't way to tempt fate and all that.

Anyway, it's been about a month since the last activation. The week after it started happening, I locked the car with the key to avoid switching on the alarm and then started to just disable the intrusion sensor before locking up on the button. I've got increasingly confident in the last couple of weeks and just (double) lock it normally.

Hopefully ColinBarber and other were correct in their predictions above and the critter is now dead.

To paraphrase Scooby Doo: Thanks for getting involved until the mystery was solved 👍

 

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