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Alarm Problem With Is200 Sportcross


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Hi, the alarm on my Sportcross is going off at random ,some times it stays set for hours before it triggers. I have read some previous posts ,and checked all the limit switches work,disconnected the interior sensor ,all to no avail .The main car Battery is new and the key fob Battery has been replaced .From previous experience with a Toyota this problem was caused by a low backup alarm Battery unit which had to be replaced .Does my Lexus have such a unit ? if so where is it located

thanks Dave

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Dave i have the exact same problem with my 200.

I have disconnected the interior sensor, bonnet catch sensor (so it thinks its always shut) changed fob Battery but still the problem persists?

Did you manage to find out if there is a back up Battery to replace?

Tbh I'll be happy with having the completely disconnected and just the remote locking working if thats possible?

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Hi no .as they say been there done that ! I feel there must be a back up as there is one on the saloon behind the side lining , at the moment I am disconnecting the door switches one at a time to see if this helps

Dave

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All my door switches seem to operate the interior light ok so i have disregarded them at the moment. Im wondering if a dodgy switch could just be causing the light to come on, cause the volt drop and cause the alarm to sound?

Suppose an easy way of testing that theory is to just remove the interior bulbs?

If the Battery is built into the boot siren i might just give another a go? They go for about £15 on eBay. (My car is the saloon)

The estate must have the same siren somewhere?

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Hi, my local auto electrician says that low voltage in the boot alarm Battery will cause these problems ,he has fitted a pattern replacement to other cars to cure the problem .When I get time I will continue looking for mine.At present I am using the key to lock up which does not arm the alarm .Let us know if replacing this unit works for you.

Dave

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  • 3 weeks later...
  • 4 weeks later...

I am also experiencing the alarm going off randomly in my 2002 IS200 SE. A few years ago there was trouble with the headlights coming on and sometimes also the alarm. The screen had not been changed and there was no sign of dampness in the fuse box in the driver's footwell. Nevertheless a hairdrier and WD40 in that area appeared to cure the problem at that time.

Now the alarm is sounding randomly, although there may be a link with wet weather. I must have read most of the threads on this - and tried the possible solutions, motion sensor, door switches, etc. I am interested in the idea of the alarm Battery being low. Can anyone please describe exactly where the alarm unit is? Also, can it be safely disconnected? At the moment I have to leave the car either unlocked or manually locked. I appreciate that alarm disable information will be sensitive so please feel free to pm any information. Disconnecting the horns unfortunately still leaves the siren.

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I fitted a replacement siren to my car over the weekend, not sure if its cured the problem or not? It seemed ok on Saturday, however i didn't trust it to leave it overnight. I rearmed it on sunday morning an it went off within 20 mins!

I'm wondering if it could just be the back up Battery in the siren needs to charge? With a week of using the car I'm hoping this might happen? I'll try again over the coming weekend.

I have also searched alot about this problem but cannot get to the bottom of my issue. Its a pain not being able to lock the car with the button, I'd settle for the alarm being deactivated and the remote locking working if i could work out how it could be done if possible?

One thing I've not tried is removing the roof lining and looking for a damaged alarm wire, purely as i see this as unlikely?

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Thanks for your reply Ben. Do we have any idea what type of Battery is used in the alarm? e.g. is it a rechargeable type or a long life lithium non-rechargeable, for example? I have no idea of the arrangement of the siren unit but Is there any reason why the Battery can't be replaced on its own? Can the siren be disconnected? I suspect that the siren unit is located somewhere behind a side panel in the boot - but which side?

I would also gladly settle for disconnecting/disabling the alarm, no matter the implications. This should be straightforward if the information is available. I am sure there will be people on the forum who know how to do this? If you had the alarm unit removed did the vehicle operate without it? If not, maybe a simple connector with a link is needed?

A lot of questions, but are there answers?

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Siren is on the drivers side / right behind the boot side panel. It is easy to get to.

I only sourced another complete siren so i could remove the original and fit replacement in one go. For £11 I thought it was worth a go.

I shall take my old unit apart and have a look to see whats inside and let you know. On the era of these cars I'd expect it to be a ni-cd or nimh?? I've always assumed its rechargeable but i really dont know?

I didn't try the car with the siren removed as i had the main Battery disconnected. I'd read in other posts of people having problems with the alarm going a bit crazy when reconnecting everything so i made sure it wasn't armed and removed the neg lead from the Battery first.

If you could simply bridge a couple of wires to bypass the alarm and retain the remote locking that would suit me down to the ground! I did contact a local auto alarm guy a while back and he suggested that as the siren and horns sound it wasn't something he thought he could easily fix and wasn't interested in looking at it.

Thing is, the problem must be traceable and fixable!

You mentioned dampness in the fuse box? I've not heard of this issue before, i will check mine

Ben

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You mentioned dampness in the fuse box? I've not heard of this issue before, i will check mine

That used to be quite a common problem, normally due to a replacement windscreen not being sealed correctly. I guess the replacement companies figured out how to do it properly now so you don't hear as much about the issue. Symptoms are headlights staying on, hazard lights playing up, alarm issues and other problems too.

Here is an example of what happens:

http://www.lexusownersclub.co.uk/forum/topic/94492-efi-relay-clicking-removed-junction-box-need-help/

this one wasn't too bad and was cleaned up. Others have had to replace the fuse box which I think costs around £180 for the part.

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Thanks to all for the additional information. Ben, I will be very interested to hear what you find inside the old siren unit - please do let us know. I agree that the details of the alarm system must be documented and known to service centres, etc. but unfortunately no-one is forthcoming on this, e.g. how to diagnose faults, how to disable, etc. We certainly have a legitimate reason for needing this kind of information! It may be a little time before I can take a further look at mine. Being a chartered electronic engineer I will be rather interested to investigate the setup.

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You mentioned dampness in the fuse box? I've not heard of this issue before, i will check mine

That used to be quite a common problem, normally due to a replacement windscreen not being sealed correctly. I guess the replacement companies figured out how to do it properly now so you don't hear as much about the issue. Symptoms are headlights staying on, hazard lights playing up, alarm issues and other problems too.

Here is an example of what happens:

http://www.lexusownersclub.co.uk/forum/topic/94492-efi-relay-clicking-removed-junction-box-need-help/

this one wasn't too bad and was cleaned up. Others have had to replace the fuse box which I think costs around £180 for the part.

Thanks for this link, i will check mine out.

Although my car appears to still have its original screen fitted and I've not had any issues other than the alarm problem?

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Thanks to all for the additional information. Ben, I will be very interested to hear what you find inside the old siren unit - please do let us know. I agree that the details of the alarm system must be documented and known to service centres, etc. but unfortunately no-one is forthcoming on this, e.g. how to diagnose faults, how to disable, etc. We certainly have a legitimate reason for needing this kind of information! It may be a little time before I can take a further look at mine. Being a chartered electronic engineer I will be rather interested to investigate the setup.

No problem Alan, i shall let you know what i find.

Sounds like you're going to understand the working of an alarm system much better than me! I am fine with the oily bits and basic electronics but after that its a bit beyond my knowledge.

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  • 1 year later...

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