Random alarm going off

So, she's an 03 prerunner 5 lugg 2wd and randomly her alarm goes off for a few seconds then stops. I've noticed no trend. Some days it's every hour and sometimes it won't happen for weeks. I don't know if these two go together but my driver door doesn't lock either.. Like it will click to lock but you can still open it after but with the alarm going off.. Even if I manually lock it but then the alarm won't go off.. I don't think think the system she has is stock. Bought her with this shitty alarm system. Any advice is appreciated!

 

Depending on the alarm, it MIGHT be tied into the power locks and/or is using the electrical system to sense when someone opens the door. Some of them look for an electrical drain to determine if someone has broken into the car. For example, the door opens, the light goes on, the electrical drain is noticed, and the alarm goes off. You'll notice that they don't put little sensors on the doors in vehicle alarms.

That said, a lower-quality after market alarm could have a short. I had one on a prior car, and it started to destroy batteries. Something about the way they installed it was always draining the battery.

It's also possible that whatever is causing the door to not lock is impacting the electrical system enough to create a short or a battery drain. If it was trying to actuate, but is stuck, maybe it's drawing from the battery and the alarm becomes convinced that someone has opened the door.

After my battery-destroying experience, I've opted for dealer-installed alarms since. Never had a problem with them. And they seem to lock themselves if I deactivate the alarm and don't open the door fast enough.

You may try fixing the door first to see if the problem goes away.

And given how old this thread is, maybe you already have...

 

Make sure there are no loose connectors going to the alarm module. Alarms can act possessed if there is a loose connector....