Car alarm randomly going off in Toyota Auris

Could be a bonnet sensor switch or maybe 12v car battery is low? A low battery can cause the alarm to go off intermittently and I've heard that a bonnet sensor switch can cause alarm issues too. (micro switch located on the bonnet catch mechanism)
 
Last edited:
Laughahalla said:
Could be a bonnet sensor switch or maybe 12v car battery is low? A low battery can cause the alarm to go off intermittently and I've heard that a bonnet sensor switch can cause alarm issues too. (micro switch located on the bonnet catch mechanism)
Click to expand...
Yea, it could be that or any number of other issues but then if it was, why would the car alarm only go off when locking or unlocking the car?

I would expect that the dealership would have investigated this when they had the car for 2 days recently. If they didn't, they'll get another chance to investigate as they have proposed to investigate the ongoing issue again later this week.
 
ivorystraws said:
why would the car alarm only go off when locking or unlocking the car?
Click to expand...
Alarms systems often run through a system check sequence when arming/ disarming.

See here:
Siren problems: Siren sounding when indicator lights are not flashing - replace siren The siren is probably the most problematic part of the alarm system, when this goes wrong it can cause some odd alarm conditions, such as going off when arming/disarming or sounding for a few seconds while driving the car. If the siren sounds for no reason (usually the indicators do not flash) e.g. while driving the car and does no respond to the remote fobs is usually an indication the unit is faulty and needs replacing. The siren for the M99T model (M11A) is no longer available
Click to expand...
 
Leo said:
Alarms systems often run through a system check sequence when arming/ disarming.

See here:
Click to expand...
Yup, they all sound familiar.... siren sounding when indicator lights not flashing, alarm sounding for up to 15 or 20 seconds while driving the car, alarm not responding to fobs.... we've experienced all of these but only after attempting to alarm/disarm the car.

If the unit was faulty and the dealership claimed they replaced the faulty unit with a new alarm unit of the same make, then, why does the problem persist?

I've no proof that the faulty alarm was replaced.
 
ivorystraws said:
If the unit was faulty and the dealership claimed they replaced the faulty unit with a new alarm unit of the same make, then, why does the problem persist?
Click to expand...
The siren and main alarm unit will be separate with the siren often placed near the front grill to allow maximum volume outside the car. They may have just replaced the main unit.

If you have the older M99 model with the discontinued siren model, it sounds like both the siren and main unit need to be replaced with the M99T2 unit and compatible siren
 
Leo said:
The siren and main alarm unit will be separate with the siren often placed near the front grill to allow maximum volume outside the car. They may have just replaced the main unit.

If you have the older M99 model with the discontinued siren model, it sounds like both the siren and main unit need to be replaced with the M99T2 unit and compatible siren
Click to expand...
You're like the Columbo of the faulty car alarm world as that does seem to be the likely cause and potential solution. I hope you don't mind but I've shared your response with the dealership to see if this information helps.

I'll let you know if you've virtually diagnosed and proposed the solution to this ongoing issue. Thanks for your help!
 
  • Like
Reactions: Leo
ivorystraws said:
I hope you don't mind but I've shared your response with the dealership to see if this information helps.
Click to expand...
No problem at all. Long time ago now but I once had a car with a temperamental after-market alarm, so I know how frustrating it can be.
 
Leo said:
No problem at all. Long time ago now but I once had a car with a temperamental after-market alarm, so I know how frustrating it can be.
Click to expand...
You're absolutely right there.... we've been out to the dealership three times now about this issue and it's at least a 1.5 hour round trip (depending on traffic) so it's extremely frustrating. At least today they had someone collect the car and provided us with a courtesy car.
 
  • Like
Reactions: Leo
I wonder could it be that the internals of the key fob are worn? Ie the switches underneath the buttons.
 
You must log in or register to reply here.
Back
Top