The Subaru Outback is one of North America’s most recognizable station wagons.
As with any vehicle, the alarm can be triggered at random times and for unknown reasons.
This article explains why your Outback alarm keeps going off, and what you can do about it.
Why Does My Subaru Outback Alarm Keep Going Off?
The Subaru Outback’s alarm can be triggered by unlocking the car manually with the key (and not using the key fob or keyless entry function), a weak or dying 12V battery, faulty alarm sensors, tailgate electrical problems, faulty key fob, or a faulty hood switch.
1. Unlocking the Car Manually With the Key (Not Using the Fob)
A common cause of a Subaru Outback alarm being triggered for unknown reasons is when owners unlock the car manually with the key (and not using the key fob). When you unlock the door with the key and open the door, the alarm will trigger. The alarm system assumes it is an intruder that’s gained access to the car.
If you have lost your fob, it is damaged, or run out of battery, you can silence the alarm with 3 on/off cycles of the ignition key within 5 seconds.
Using your fob for lock/unlock will not set the alarm off.
Here’s what owners had to say about this on the subaruoutback.org forum:
“No switch on the back of the door lock cylinders so if you don’t unlock the car with the remote, it has no idea that it’s a legit opening. Buy a remote and program it in and use it or put your car in valet mode if it bothers you. Many, many car manufacturers do this. . . to the dismay of many, many owners.”
“I think the deal is – if you lock it with the remote, you have to unlock it with the remote because the remote enables the alarm. If you lock it manually or with the key, you don’t set the alarm so you can unlock it any way you want.”
2. Weak or Dying 12V Battery
When a 12V car battery is weak or dying, it has an insufficient power supply (or voltage), and this can trigger the Outback’s alarm. This is more likely to occur if the battery is old or has not been properly maintained. In fact, it is the leading cause of false alarms and random alarm activity.
Dirty/Loose Terminal Connections
You can clean the battery yourself. If your battery is older and hasn’t been cleaned, this would be the first place to start diagnosing the cause of your Outback’s false alarms.
Disconnect the battery’s terminals (make sure the engine is not running), and scrub them with a toothbrush dipped in baking soda and water mixture.
Be sure to dry off any excess water or moisture from the terminals before reconnecting your battery.
When reconnecting the battery, ensure the connections are tight and free of any obstructions on the terminals.
Old/Faulty 12V Battery
A Subaru Outback’s 12V battery usually lasts 3 to 5 years before needing replacement.
Before zipping off to your nearest AutoZone, pop open your Outback’s hood to check the battery’s health condition.
You can quickly check the battery if you have a multimeter in your garage (instructions at the end of the bottom of the article).
Alternatively, drive to your nearest AutoZone – they offer free battery health checks.
One owner on the subaruoutback.org forum posted this helpful insight for another user who experienced a dead battery in their Outback:
“I agree, the battery could be badly sulfated from sitting discharged for a long period of time. You might be able to resurrect it by charging it very slowly with a trickle charger for several days. Failing that, it needs to be replaced. The alarm is acting whacko because it is getting powered to some low, odd voltage it was never designed to work at.”
3. Tailgate Electrical Problems
On new and older generations of the Subaru Outback, the tailgate sometimes causes hassles for owners.
The tailgate shows as ‘open’ on the dashboard when it is closed and locked.
This causes the alarm to go off – even when driving.
To make matters even more confusing, the Outback will show that the tailgate is closed and locked when in fact, it isn’t.
When the owner parks the car, the tailgate is unlocked, and the alarm gets triggered.
Here is more information from owners on the subaruoutback.org forum:
“I had a similar issue with the alarm going off randomly when the car would be parked and locked. It turned out to be the rear gate lock that started to malfunction, and then the alarm would probably think that, while the car was locked, someone had broken in through the gate. I disconnected the electrical switch of the gate lock for the problem to go away.”
“2022 Outback wilderness here. So I was in the store, and when I came out the security alarm on my car was going off, but nothing seemed to have been touched or anything. I hit lock or unlock to cancel the alarm, started my car, and it said the back hatch was open, even though it wasn’t, I tried to open it and it wouldn’t do the power liftgate, so I had to hold down the button and then it opened, I was able to close it, but then it says it’s still open. All of my interior lights are on because of it. Is anyone had something like this happen and know how to fix it? The manual refers to a process that is not working.”
The solution is to reset the rear lift tailgate function to clear the alarm’s false triggers.
An owner on the subaruoutback.org forum shared the procedure to do that:
- Owner’s manual page 157 says that if the rear liftgate is closed, the reset procedure is:
- Keep pressing the rear gate opener button until it is unlocked (I assume this means on the tailgate and not the remote).
- Lift up the rear gate.
- Pull down the rear gate until it starts to close automatically.
- The system will be initialized once the gate is fully closed.
- Check that the power rear gate operates correctly.”
If problems continue its best to take your vehicle to your nearest dealer and have them take a look
4. Faulty Key Fob
A faulty key fob can trigger the Outback’s alarm randomly. If your key fob is dirty or needs a replacement battery, it can also trigger the Outback’s alarm system with a false alarm.
Open your key fob, and remove any dirt or debris that may be inside the fob using.
Remove the battery, and clean those terminals with some rubbing alcohol and a soft cloth.
If the alarm continues to be triggered, perhaps you should change the key fob’s battery.
These are relatively cheap, although its worth spendin a little extra for a good quality battery.
If the alarm still goes off, you may need to contact your dealer or an auto-electrician in your area.
5. Faulty or Dirty Hood Switch
The Outback has a hood switch which is designed to trigger an alarm if someone tries to force open the hood – if it is broken or dirty it can cause the alarm to go off. This switch is also known as a hood latch sensor.
Dirty / Corroded Hood Switch
Due to the location of the hood switch, its not uncommon for it to get very dirty – this alone is enough to trigger the alarm at random. Corrosion and rusting of the hood switch is also very common, which can also trigger the alarm.
The first thing you should do is give the hood latch a thorough clean to remove any gunk buildup and spray a little WD40 for lubrication.
Faulty Hood Switch
It’s common for the hood switch (hood latch sensor) to get damaged or fail completely.
If the switch that monitors whether the hood is open or shut isn’t working then this can trigger the alarm.
Replacing the hood switch is a fairly cheap and easy process, however if you are not mechanically inclined, have your local dealer replace it for you.
6. Faulty Alarm Sensors
Faulty alarm sensors are another common causes of false alarms in Outbacks.
The Subaru Outback has a number of alarm sensors that are designed to detect movement within the cabin of the car as well as the exterior of the vehicle.
These are mostly located in the doors, tailgate and hood etc.
If one of these sensors is faulty, it can trigger the alarm system even when there is no threat to the vehicle.
Your local Subaru dealer should be able to pinpoint which one with diagnostic testing.
Related: 8 Most Common Subaru Outback Problems (Explained)
Disconnect the Battery
Sometimes mysterious alarm problems can disappear with a simple reboot, there are no guarantees here but it’s worth a try.
Disconnect the battery for 20 seconds and this resets many of the electronics in the vehicle.
Pull the Horn Fuse
On some Subaru Outback models by pulling the horn fuse you disable the alarm temporarily until you find a solution.
Check For Warning Messages
When the alarm occurs can you see any lights or warning messages on the instrument panel?
This can give a clue as to what’s causing the alarm e.g. ‘Hood Ajar’.
Take it to a Subaru Dealership
If needed, take your Subaru 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 Chevrolet 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 Subaru’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, it may also be related to why your alarm keeps going off.
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.
Test the 12V Battery
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 car 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.