Alarm goes off sporadically, even when not set

Highlander Limited, 2010, alarm goes off sporadically after driving. Lately, it has even gone off WITHOUT being set! Anyone have any suggestions? The dealer can’t find any codes nor causes!

Is this a factory alarm or an aftermarket alarm?

Does anyone near the car have the keys in a pocket at the time? Maybe the panic button is getting pressed accidentally.

Exchanging the alarm system may be the easiest way to see if the trouble is internal with the system, which it sounds like may be the case here.

Factory, and no longer made. Specifically laid remote on counter to be sure wasn’t being caused by panic button accidentally being pressed. Dealership has no idea.

You should be able to find OEM replacements through salvage yards or places that sell refurbished electronic auto parts at prices that are a lot lower than what dealer new prices would have been.

Just have the alarm disabled, most of the time they are ignored anyway.

Are any of the door open/closed switches acting up? Does the dome light come on when it isn’t supposed to, or the door open icon on the dashboard appear intermittently for no apparent reason? If so, that’s probably a good guess where to start looking, a defective door switch. It may just need its contacts cleaned.

There is a service bulletin that applies to some 2010 Highlanders, the security alarm may falsely activate due to a faulty hood switch.

If the doors are not locked when the alarm sounds then the bulletin does not apply, this would suggest the panic alarm is sounding. Look in the vehicle for a lost key/transmitter.

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No switch/door/dome light problems. The dealership checked all the switches and found no problems.


@dennis.moore14 Do you realize that your name and email show up on the post when you reply by email?

what does the owner’s manual say are the things that are designed to cause the alarm to go off? There should be a list, such as: Opening a door, opening the trunk or tailgate, opening the hood, someone touching the a metal part of the car, someone coming into proximity with the car, disconnecting power to the alarm, etc … If you want to figure this out yourself you’ll have to come up with that list, then eliminate the potential causes one by one.

hi I have the same problem with my 2008. It is the factory installed basic alarm. if I do not lock the doors they lock automatically. I took it to the dealer who basically blew me off… it did go off when there, in a three football field dealership lot… Any, did you find a solution? it may be a faulty sensor on one of the locks, but i’d rather they just disconnect the alarm from the horn and lights; if I can find someone to do it rather than for the repair shop to go on a wild goose hunt replacing sensors one at a time.


After I get out, I no longer have the issue. Now it happens after it sits in the garage, usually overnight, no alarm set, and the alarm will go off if I don’t start it after getting in.

I have found that if you “unlock” with the key fob, if you don’t get in (open a door), it will automatically lock. Got same blowoff from dealership-factory-installed alarm no longer made, etc, etc.

Repeating previous post. You should edit out your email address just because it is a good thing to do.

How do I do that.

Click on the slanted pencil looking icon at the bottom of your post and you can edit .

There isn’t one on that one.

@cdaquila Carolyn, could you remove the email address on post #9 for Dennis please.