Alarm sets itself - maybe draining battery? Need Help!

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FiveFlat

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My LS is parked in my garage. I can be in there working on something and all of a sudden the lights blink on it like the alarm is set, but the doors stay unlocked. If I open the door, the horn goes off. What could be causing this to set itself?

Also, after that started happening, about 3 months the battery started dieing and I have to stick it on a charger. Now, I don't want to go buy a new battery(which I'm sure I'll need to do) until I get this electrical/alarm issue dealt with first.

Any ideas?
 
FiveFlat said:
My LS is parked in my garage. I can be in there working on something and all of a sudden the lights blink on it like the alarm is set, but the doors stay unlocked. If I open the door, the horn goes off. What could be causing this to set itself?

Also, after that started happening, about 3 months the battery started dieing and I have to stick it on a charger. Now, I don't want to go buy a new battery(which I'm sure I'll need to do) until I get this electrical/alarm issue dealt with first.

Any ideas?
Click to expand...

I have a friend that has this problem on his BMW. What makes his happen is if hes window is open and he sticks his hand in side while the doors are closed. idk if our cars are anything like the bmw's as far as the security goes tho..:confused:
 
This could be happening because your battery is low/bad. Otherwise, it could be a problem with the FEM or the wiring to it.
 
is there an aftermarket alarm on it, if so it could be set to passive arm (the car arms itself a minute or so after the dome light goes off)

and remember if you didn't buy the car new, just because you dont think there is an aftermarket alarm on it doesn't mean that there is not one :)
 
1LoudLS said:
is there an aftermarket alarm on it, if so it could be set to passive arm (the car arms itself a minute or so after the dome light goes off)

and remember if you didn't buy the car new, just because you dont think there is an aftermarket alarm on it doesn't mean that there is not one :)
Click to expand...

i was going to ask the same question. when i had my alarm newly installed it did something similar. i would lock it and then it would unlock itself after a while because of how my installer installed the alarm by tapping into the front driver locking mechanism. just make sure you have a factory alarm
 
I did buy the car new and never installed an aftermarket alarm. This is the factory anti-theft system. From what I understood was it's not really an "active" alarm that you can arm. But it's likely I just don't understand this factory system all that well.

I hope you're right about the Low voltage crashing the microprocessors. I'll buy a new battery and see if that helps...
Thanks!
 
Well, I bought a new factory motorcraft battery, replaced it and I still have the problem. I need some help before I waste this battery too.

What is the FEM? Where should I go from here?
 
FiveFlat said:
Excellent! Thank you very much for that link. Now I don't have a tuner or anything on my car that can read DTCs Can I just pickup an inexpensive one at Kragen autoparts? Also, I thought that if there were any codes, the check engine light would be on. It's not. Am I wrong?
Click to expand...

Generic scanners will only read the government mandated emissions codes. You need a Ford specific (also CAN specific) scanner that will read all the other data and codes. No, your check engine light doesn't have to be on. For example, you could read out failure codes stored in the climate control system. A climate control fault doesn't turn the check engine light on, it wouldn't make sense for it to.
The factory perimeter alarm system is software that runs on the FEM (Front Electronics Module) and the REM (Rear Electronics Module). A Ford specific scanner (usually around $400) would let you read any trouble codes from those modules. The more expensive test/scan systems ($1000 +) would let you send commands to those modules to make it easier to test the signal lines to try and find the problem.

As a practical matter, if you are doing this (and not a dealer), you may have to settle for close inspection of all the wiring, connectors, and switches involved.
 
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