The Ascent is the biggest Subaru sold today, making it a great family choice.
As with any vehicle, its alarm may go off randomly and for unknown reasons.
If your Ascent alarm keeps going off, this article will help you diagnose the cause and help you to resolve it.
Why Does My Subaru Ascent Alarm Keep Going Off?
The Subaru Ascent’s alarm can be triggered by a dying or weak 12V battery, powerlift tailgate issues, a faulty key fob, unlocking the car manually with the key (not using the key fob), and accidentally pressing the alarm button on the key fob.
1. Dying or Weak 12V Battery
If the 12V battery is dying or has an insufficient voltage, it can trigger the Ascent’s alarm.
This is a leading cause of intermittent false alarms and mysterious nuisance alarms.
A 12V battery usually last 3 – 5 years before needing to be replaced.
Before swapping the battery, inspecting the one under your Ascent’s hood is worthwhile.
A loose or faulty connection can also cause the battery to malfunction.
If you have a multimeter, check the battery yourself.
If not, head to your nearest AutoZone – they offer free battery health checks.
You can also try disconnecting the battery, cleaning the battery’s terminals, and then reconnecting the battery.
When reconnecting the battery, ensure the connections are tight and free of any obstructions on the terminals.
You can clean the terminals of your 12V battery using a toothbrush dipped in baking soda and water mixture.
2. Powerlift Tailgate Issues
The alarm on the Ascent’s powerlift tailgate can cause false alarms, be triggered for mysterious reasons, or malfunction. Many owners have reported they have been able to rectify this issue by disconnecting and reconnecting the battery.
One owner posted on AscentForums.com about this powerlift tailgate problem triggering the alarm:
“I have a Premium with the power lift gate, last night I pulled into my driveway, hit the button on the dashboard to open the lift gate, it did not open and an ear piercing alarm (from the rear of the car) went off. I could do nothing to open the rear door or stop the alarm, the fob did not work, the button of the read door handle did nothing. I had to disconnect the battery to get the alarm to stop. When I reconnected the battery the door worked as it should and no alarm.”
One owner on Reddit shared a similar story:
“It happened to us Dec 24th 2019. I disconnected the battery too to resolve. A video on YouTube stated it was Fuse 14. Might be a TSB for it Power Lift Gate.”
On the forum JustAnswer.com, another Ascent owner posted about their experience with this problem:
“My 2020 Subaru Ascent truck is stuck and the alarm is going off. I removed everything from my trunk that might block it.”
The mechanic on JustAnswer.com responded to the query:
“Make sure all the doors are unlocked then go to the rear of the vehicle and press and hold the button above the license plate until you hear the rear gate latch move, this could take 30-45 seconds. Once you hear this movement you should be able to raise the gate manually, raise it fully then lower it manually until it rests on the striker from here it should close and latch on its own and be fully reset.”
If the problem persisted after that, the mechanic shared that the owner must disconnect the battery for a few minutes before reconnecting it and then retrying the above-mentioned procedure.
3. Faulty Key Fob
A key fob that is dirty, damaged, faulty, or needs a replacement battery can trigger your Ascent’s alarm to go off randomly.
Dirty Key Fob Internals
Open your key fob (as if to replace the battery) and clean any dirt, grime, and grit that may have entered the device.
Clean the battery contacts carefully with some rubbing alcohol and a soft cloth.
Key Fob Battery Replacement
After you’ve closed the key fob and the alarm is still triggered, you should change the key fob’s battery.
These key fob batteries are cheap to buy and will save you lots of sleep and worries.
Once you’ve replaced the battery, try to lock and unlock your car using the key fob. If the alarm still goes off, you may need to contact your dealer or an auto-electrician.
If you have a spare key fob, you can test that to see if the same problem occurs.
If the second key fob is working and the alarm is not going off randomly, there could be an issue with the programming.
The dealer or an auto-electrician can reprogram the key fob in minutes.
4. Unlocking the Car Manually with the key (Not Using the Key Fob)
Another common cause of the alarm going off randomly for Subaru Ascent owners is unlocking the car manually with the key and not the key fob.
If you have unlocked your Ascent manually using the manual key, then this will trigger the alarm.
The Ascent’s alarm system is designed to be deactivated with the key fob, not the key.
When you lock the car with the key fob and then unlock the door with the actual key and open the door, the Ascent’s alarm system suspects that the vehicle is being broken into by an intruder.
You can silence the alarm by turning the key in the ignition to the ‘ACC’ position.
5. Accidentally Pressing the Alarm Button on the Key Fob
A common yet overlooked reason why an Ascent alarm goes off at random is due to owners accidentally pressing the alarm button on their key fob.
When the key fob is in your pocket – and especially when it is on a ring with other keys and key ring charms – the alarm button on the key fob can be accidentally pressed.
An Ascent owner shares their experience with accidentally pressing button (albeit not the alarm button):
“I’ve had many key-less cars before, BMW, Mercedes, Cadillac, Ford, Toyota etc and I have never had an issue with any key fob such as this before. Never! The issue is I keep finding my car unlocked at times. (Driver Door and sometimes all doors). Nothing has ever been missing out of the car and I doubt someone else has an identical fob as this has also happened at other locations other than where I live. I have isolated the problem to my key fob actuating while it’s in my pocket. It’s happened about 8 or 9 times already. I’ve always carried my key fobs in my same pocket all by itself, nothing else in there and never had a problem.”
6. Hood Latch Sensor Issues
The hood latch sensor 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.
Dirty / Rusted 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.
Its a good idea to give the hood latch a thorough clean to remove any gunk buildup.
It’s also a good idea to spray a little WD40 too lubrication.
Faulty Hood Switch
It’s not uncommon for the hood switch 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.
Related: 5 Best & Worst Subaru Ascent Years (With Pictures)
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.
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.
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.