sMEGMATRON

Hey guys i've owned my 94LS400 for about 5-6 years now, and i've never had a fob with it so a faulty fob couldnt be the issue. Up until about 2years of owning it, i never knew if the alarm worked or if it even had one tbh, but when i first found out it did, my coworkers had to tell me that my cars alarm is going off. I ran out, put my key in the door and the alarm stopped as soon as it unlocked. i didnt thjink much of it. (since i live in WA state and we have trees everywhere so i figured it would be safe to assume a branch or pinecone broke off and hit it.) About a week or 2 later it happened again, but the weather this day was a bit different since it was raining. but even when the rain stopped the alarm kept being trigggered and thats when i started trying to open doors and got really physical with it and nothing seem to trigger it. the only way i got it to trigger from the outside is if i opened the trunk with the key, and then closed it. (alarm doesnt get triggered when opened, but goes off when it gets closed. The alarm doesnt even work for the hood opening and closing) So i decided to run some experiments on my day off, i left a window down and locked it. and everything i do on the inside seems to trigger it like it should. except the hood ,trunk, and gas latch. if i put the key in the ignition and started it, it would start right up.

Since that incident at work i've, replaced the battery, alternator, and i cleaned off the terminals and made sure connnection was good but it kept coming back every other month or so. and with the car being almost as old as me, i kept running into more issues. and every time i fixed an issue, another would appear with no check engine light. So, being unable to pull codes from it, I said, "FUGGIT, ECU it is." So, i got a new one (couldve bought a gas saver for less at the time, since this was about a year before covid hit,) and havent had a single issue with the LS until monday.. Where i had to run out my house about 8 times within an hour to turn the alarm off. so, i disconnected the battery for the rest of the day and reconnected it that night. She's been quiet until today. i woke up, made a cup of coffee, and started to get my day going when i hear the alarm going off again.

now, im stuck trying figure out what it can be .. Can someone point me to where i should start this time?

CELSI0R

I suspect an electrical issue, perhaps with one of the door switches. It could be flaky and then cause the alarm to go off when it shakes. However, this has to be tested. I would not go swapping out this part without checking the system first

Do you notice if this happens more when it's hot, too?

I think the problem disappearing while you had the new ECU was a coincidence, but really did not have much of an effect in solving the problem.

Attached are some 1993-1994 troubleshooting docs. It sounds like you've already gone through most of testing the system from the first page

It's important to note the status of the security light on the dash, when the system is set.

You can disconnect the connectors for the front horns on your car so that only the small security horn (next to the cruise control unit) goes off and you wont have to suffer (like how my hearing has already).

cyfi66

There is a sensor inside each door lock actuator that senses if the door is locked or unlocked. If the connection is bad then it will trip the alarm randomly.

Lock and unlock the doors with the drivers switch and see if any of the actuators look weak. One of my rear ones looked weak, like it couldnt switch back and forth all the way. After I replaced that one the alarm stopped going off randomly.