The F-150 is the number one selling vehicle in the US and has been for over four decades.
Like any other vehicle, it’s not uncommon for the alarm to develop problems and go off at random.
If you’re Ford F-150 alarm keeps going off this article is here to help.
Why Does My Ford F-150 Alarm Keep Going Off?
The most common cause of the alarm going off on an F-150 is due to the interior motion sensors however there is a TSB on some models which requires a software update. Other causes include high shock sensitivity, low key fob battery, faulty hood switch and a low 12V battery.
If your F-150 alarm is going off when it shouldn’t then by process of elimination, it shouldn’t be too tricky to narrow down the root cause.
1. Interior Motion Sensors
A very common cause of the F-150 alarm going off is linked to the interior motion sensors.
The idea behind these is that it lets you keep your window open – but the alarm will go off if someone reaches in your truck to steal something like you’re phone or iPad – the sensors are aimed at and are monitoring the four windows.
The sensors are located in the roof console, two on the left and two on the right, in a square formation – they are round/circular looking and run in line with the roof console lights.
Sometimes insects and bugs might get trapped in the truck or even leaves being blown in, which can be picked up by these sensors thereby triggering the alarm.
Some owners have complained that after leaving their dog in the truck they’ve come back to find the alarm going off.
Give it a week of not arming the interior sensors by selecting the ‘Perimeter’ option, push ‘Ok’ to set. You will have to do this each time you turn off / exit the truck, and see if this stops the alarm from going off.
Note: If nothing is selected the truck will default to both interior and exterior sensors every time. It is not possible to default to ‘Perimeter’.
In Advanced Settings/Vehicle, you can select 1 of 3 choices:
- All Sensors (turns on the interior sensors)
- Prompt every time
If you’re often leaving dogs inside, ‘Prompt Every Time’ which is the same as ‘ask on exit’ is probably the best option.
As soon as you turn the truck off, you can use the up/down arrows on the steering wheel to select the appropriate mode for that cycle.
Alternatively, you could cover the sensors over with something like electrical tape.
2. Body Control Module Update
The BCM or Body Control Module is a control unit that is responsible for monitoring and controlling all other electronic systems in your truck, such as security systems, electric locks, lights, power mirrors, and air conditioning systems etc.
There is a known issue with some 2021 F-150 trucks which ultimately causes the alarm to activate when there is no sign of an intrusion.
Ford Issued a TSB for this issue: TSB #SSM 49601
If you suspect you’ve been affected by this you’ll need to take your truck to your dealer and have the BCM updated to the latest software.
3. Shock Sensor Sensitivty
On the F-150 there is often a shock sensor connected to the factory alarm – if the sensitivity is turned all the way up, then the alarm will go off very easily.
Shock sensors detect hits and impacts around your truck, e.g. if someone breaks a window the sensor detects this and sends a signal to the alarm’s computer.
The sensitivity setting for this alarm should be mounted to the driver’s side vent tube.
Open the door and remove the access panel on the side of the dash.
There will be a black box mounted with zip ties.
There should be a little black knob with white markings in a half-moon shape around – this controls the sensitivity. It looks a bit like a volume control knob.
Failing that look under the dash – the backside of the OBD-II port should have another connector that it’s plugged into, probably zip-tied to it.
If so, follow it up to the Vehicle Speed Sensor (black box), it shouldn’t be more than a foot away.
If you can’t find the control knob then you may have a system that will need to be programmed in order to adjust sensitivty, in which case you’ll have to get the dealer to turn down the sensitivity.
4. Faulty Hood Latch Sensor
A common cause of the alarm going off on the Ford F-150 is due to a faulty hood latch sensor otherwise known as a hood switch.
Due to their location, hood switches often get dirty and clogged up so it’s worth giving it a clean and some lube first.
The hood sensor is a simple electrical switch, that monitors whether the hood is open or closed.
You may even notice a hood ajar message pop up when you’re driving.
If the sensor completely fails you may see the hood ajar message constantly on.
If you suspect the hood switch is faulty and your truck is still under warranty we recommend taking it to the dealer and having them replace it for free.
If you’re mechanically inclined you can simply replace the hood switch yourself, these can be picked up for $40 – $80.
One owner on f150forum.com had this to say:
“With some simple diagnostics I discovered it was the flimsy bracket that holds the switch had over the years bent down far enough that when the hood was down, it wasn’t pushing the button down far enough. I was able to bend it back up by hand. To not take any more chances, I taped the button down with duct tape. Problem solved.”
5. Dying 12V Battery
A dying 12V battery or a battery with insufficient voltage can cause a wide range of problems, including triggering the alarm.
Most 12V car batteries last about 3-4 years so it might be time for a replacement, it’s worth cleaning the terminals first though and making sure the connections are tight and free from dirt and debris.
Tip: Clean the terminals using a toothbrush dipped in baking soda and water mixture
The next step is to check the battery, you can do this with a multimeter.
How to Test the Battery
- Before testing, remove the surface charge from the battery, this allows for an accurate reading.
- Simply turn on the headlights for 2 minutes then turn off.
- Set the multimeter dial to the ’20 Volts’ setting.
- Make sure the truck is turned OFF
The multimeter will have a red probe and a black probe:
The red probe is for making contact with the positive terminal
The black probe is for making contact with the negative terminal.
Measure across the battery terminals.
The meter should display a reading, if the battery is fully charged the voltage should be between 12.2 and 12.6 volts.
Anything under 12V and the battery should be charged or replaced.
If you’re not confident doing this, take your truck to any AutoZone who often offers free battery health checks.
6. Low Transponder Key Battery
A low key fob battery can trigger the alarm on F-150s to go off at random.
Try using your spare coded key – if the problem goes away then you know you’ll need to replace the battery in your primary key fob.
It’s advised that you don’t carry big metal objects, electronics or a second coded key on the same keyring as your primary key fob as this can lead to problems starting your F-150.
It might also be worth giving the inside of your key fob a clean as these can get filled with dirt which could be causing the alarm issue.
7. High Voltage Power Lines
Parking underneath overhead power lines can trigger the alarm on your Ford F-150.
This phenomenon is caused by electromagnetic radiation (EMR) which can interfere with the electronics on your alarm system.
If you suspect this is the cause, simply park somewhere else out the way.
Depending on where you live this may not be relevant as power lines can often be located underground.
8. Faulty Door Lock Sensors
A faulty door latch sensor is a common cause of F-150 alarms going off.
Similar to the hood latch sensor, your F-150’s alarm monitors the doors to make sure no one is opening them.
It’s a good idea to give all door latches a clean and some lubrication with WD-40.
If you suspect the door lock sensor is faulty and your truck is still under warranty we recommend taking it to the dealer and having them replace it for free.
Disconnect the Battery
Sometimes mysterious alarm problems can disappear with a simple reboot, there are no guarantees here but it’s worth a shot.
Disconnect the battery for 20 seconds and this resets many of the electronics in the vehicle.
Check For Warning Messages
When the alarm occurs can you see any lights or warning messages on the gauge cluster?
This can give a clue as to what’s causing the alarm e.g. ‘Hood Ajar’.
Take it to a Ford Dealership
If needed, take your Ford to the dealership.
Tell them you are NOT paying for a check on what the problem might be.
Ask them if they will check it for free.
Most dealerships and other places do quick/initial diagnosis for no money as they plan to make money for the repair of your vehicle.
If you’re Ford is still under warranty then they should fix and resolve the issue for free.
Check for Recalls or TSBs:
By entering your car’s VIN number on Ford’s recall page or the NTHSA’s Safety Issues & Recalls page you can determine whether or not there is a TSB or recall for your vehicle and if there is you’ll want to get it addressed.
A recall is issued by a vehicle manufacturer for issues that are safety-related, while a TSB covers components that may be malfunctioning but don’t compromise the safety of the vehicle.