Faulty Ford factory car alarm - is there a solution?

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Deal Addict
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Nov 15, 2005
1285 posts
Medicine Hat and SW …

Faulty Ford factory car alarm - is there a solution?

Allow me to vent about a really frustrating problem, one no doubt responsible for my neighbours hating me on many occasions.

Ever since my 2015 Ford F-150 was practically new, the damn vehicle alarm has been going off for no apparent reason. When it was under warranty, the dealership could never offer any solution, telling me to bring it back in "the next time it happens". The big problem with that is "next time" might be year from then, it might be multiple times that same night. They check to see what set the alarm off and it is always a "perimeter" alarm. I've never been able to intentionally set the alarm off myself by rocking the vehicle or knocking on the windows. Before the vehicle warranty expired I asked them to make a note that I have reported the problem several times and no solution was ever found - a note that they now claim to have no record of.

In any event they've never indicated that there is any real solution to this issue. I've written to Ford customer service and they are not willing to do anything now that the vehicle is out of warranty. BTW, whenever you turn off the vehicle there is a message asking if you want to set just the perimeter alarm or all alarms (which is the default and while the default can supposedly be changed in vehicle settings, it always reverts to "all alarms". This is probably a moot point since all the dealership checks indicated that it is the perimeter alarm going off. )

I estimate the alarm has gone off for no reason maybe 3 dozen times in the 5 years I've owned it - not a huge amount but those are only the times I've heard it myself and I can only imagine all the other times when I haven't been around to hear it. It almost always happens late at night and almost always in my driveway in the City although it has happened at other times and locals. It has gone off several times in the same week and once it didn't go off again for nearly a year. Lately it's been happening more frequently and I leave the truck unlocked most of the time. And let me tell you the horn on the current F-150 is LOUD.

So yes, I can leave my truck unlocked - which I must do whenever the alarm goes off because if I don't it will typically go off again after being disabled a few hours later. But I generally keep tools and other fairly expensive items in it and while my neighbourhood is a pretty good one, I'm obviously not always parked in my driveway. I could disable the horn (there's a fuse for it) but I'm one of those rare people who actually need to use the horn sometimes (typically herding cattle). I guess what I'm going to have to do is install another horn with a separate switch but that seems so ghetto.
4 replies
Deal Guru
Feb 9, 2006
12775 posts
Pete_Coach wrote: Disconnect it?
You usually can't it's built in to the factory BCM. It likely could be "Coded" off tho.

OP you likely have a faulty "Perimeter" sensor somewhere.
My money is on the hood latch.

First of all your Dealer is a POS if they can't diagnose this.

All they had to do was keep the car for a little while and plug a scanner in. The car will tell you exactly this sensor shows the fault. Can't remember if Ford BCMs store the last open sensor in their memory. I know GM And Toyota shows it in their factory scan tools.

The Shadetree way to test it is to unplug the harness and put in the correct resistor value and see if it goes off. If it stops then you know it's the hood latch that needs to be replaced. If not then you need to repeat this for each Perimeter sensor. ... on-410471/
Even shows taping over the ultra sonic sensors. Sometimes something dumb like a loud dog bark can set off the ultra sonic sensors.

It's always 50% of the time it's the hood latch sensor just because it's the one most exposed to the elements and people tend to slam hoods more than doors.
Deal Addict
Nov 6, 2014
1183 posts
0 downvotes (Maple,O…
I would guess one of the four door latches has a faulty internal sensor that goes off when in the locked position. Just a guess, but replacing all four wouldn't be cheap. You could diagnose it yourself by disconnecting one at a time and lock the car until the alarm stop triggering. Good luck.
Deal Addict
Feb 6, 2011
1928 posts
With a proper scan tool you can see the last 5 alarm events, what triggered it. Then concentrate on that switch or sensor.


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