I have an Avensis (53 Plate) and it seems to have developed a problem with the alarm system. The alarm is going off intermittently, I can reset and it goes off ten minutes later, sometimes an hour later, and sometimes hours later. I have no idea what is wrong, anybody had this problem before, or how I can diagnose the problem. I have a feeling that putting it into the dealer will cost a fortune, as the fault is intermittent, so that's a last resort.
When the alarm is going off, is there a door ajar light on the dashboard? Perhaps a door or hood/bonnet sensor is malfunctioning or isn't closed completely, setting off the alarm.
Are there any corresponding loud sounds in the area? if there's a glass breakage sensor, they can be set too sensitively, and a plane overhead or thunder can set it off.
Is there a way you can keep your keyfobs further away from your car for testing purposes? Perhaps the "panic" button on your keyfob is depressing and setting off the alarm.
Some alarms have an internal motion sensor. Do you have a rodent problem or some other thing moving in your vehicle to set off the alarm?
Do you park near some form of radio transmitter? (police/fire station, military base, broadcast TV/radio station, etc.) Sometimes they may operate at a frequency similar to that of your keyfob, and activate the "panic" alarm. Similarily, is there another car in your neighborhood with the same random alarm problem? perhaps you share a similar keyfob frequency with that other car.
I was thinking that perhaps the panic button on the key was being depressed from being jammed in someone's pocket. If the alarm is not a false alarm, then I don't know what is going on.
My 2003 Avensis has a similar random alarm fault - goes off any time of day or night even after disabling the alarm using the overhead alarm button. Not being triggered by movement in car or nearby, not by loud noises, not by close proximity of key fob. Not yet solved but looking v hard now or it has to go to a garage and as its intermittent electrical fault I'd expect a large bill. So - from looking around the forums there seem to be just two likely explanations - (1) faulty bonnet switch/ bonnet not properly fitted (plausible as my bonnet was removed/ refitted and I think it is a bit higher than originally and (2) faulty sensor switch inside car - but this seems less likely as the disabling switch did seem to work for a while. And here's a thought - if it was the bonnet catch
- would it be prevented from triggering the alarm by using the overhead alarm disabling switch which might only disable the interior sensors leaving the bonnet sensor active?
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