The Tucson is Hyundai’s best-selling model.
Like most modern cars, it is fitted with an alarm system that can sometimes go off at random, for various reasons.
If you’re Tucson alarm keeps going off, this article is here to help.
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Why Does My Hyundai Tucson Alarm Keep Going Off?
The most common cause of an alarm going off on a Hyundai Tucson is the rear occupant alert being triggered. Other common causes include key fob issues, a dying 12V battery, sensor issues or electrical issues.
1. Rear Occupant Alert
The most common reason why a Hyundai Tucson alarm goes off at random is due to the rear occupant alert being triggered.
The system is designed to prevent children from being accidentally forgotten in the car (risk of heatstroke) or accidentally being locked in the car.
- Ultrasonic sensor detects movement in the rear seats
- Horn sounds, lights flash and a Blue Link alert message is sent to the driver’s smartphone if movement is detected
If you park and then lock your car with the windows or sunroof open a gust of breeze can trigger the sensors and set the alarm off.
Or if you have left your dog in the car this will also cause the rear occupant alert to be triggered.
You can simply turn off the rear occupant alert to prevent this from happening.
Here is what the manual says:
Make sure that all the windows are closed. If the window is open, the alert may operate by the sensor detecting an unintended movement (e.g. wind or bugs)
Here’s what Tucson owners on Reddit had to say:
“It is most likely your rear occupant alert. Sounds like you probably just need to turn it off. The air blowing past the ultrasonic sensors because you left the windows open will trigger the alert.”
“So far so good. Thanks again!”
How to Disable Rear Occupant Alert
You can disable the rear occupant alert on the display screen.
- Select “Setup”
- Select “Vehicle”
- Select “Convenience”
- Untick “Rear Occupant Alert”
One Tucson owner had this to say on Reddit:
“Thanks! I figured it out now too. I was looking for an answer on the main screen, but its the screen on the main dash (that’s navigated on the steering wheel), that can get you into Convenience, then the Back Seat Alert, which can be disabled.”
2. Bug Inside Cabin
If there is a bug trapped inside the cabin and you have the rear occupant alert turned on, then this can trigger the alarm to go off.
The ultrasonic sensors are very sensitive and even a small fly trapped inside is enough to trigger them.
On Tucson-Forum.com here is what one owner had to say:
“Problem solved, it was a bug. Not with the software but an insect that made its home in the cabin. This morning I found it dead in the driver’s footwell and since no alarm. Boy these sensors are sensitive, never had this problem with any other car.”
3. Key Fob Dirty, Damaged or Low Battery
A common reason why a Tucson alarm goes off at random is due to a faulty key fob or a key fob with a low battery.
The first thing to try is changing the fob battery, avoid using cheap batteries and make sure the battery is inserted the right way up.
When you have the fob open you should also give the inside a good clean.
Dirt and dust can accumulate causing issues with the electrical contacts.
You can do this with a cotton swab and some rubbing alcohol.
If this hasn’t worked, try using a spare key fob but make sure that the other key fob is well out of range.
You should also ensure the spare fob is clean and has a fresh battery.
4. Low or Faulty 12V Battery
A low of faulty 12V battery can cause a wide range issues, including triggering the alarm at random times.
To rule this out, simply have a battery health test – this can be done by your local dealer, mechanic or even free of charge at an AutoZone.
You can also do this yourself with a multimeter, we’ve included a simple guide at the bottom of this article.
The battery should not have less than 12V.
It is also highly recommended that you give the battery terminals a good clean using a toothbrush dipped in a baking soda and water mixture and ensure the terminals are tight and free from gunk, debris, corrosion and dirt.
Similarly, if your Tucson has rusted battery terminals this can cause alarm issues as it will be unable to deliver the correct electrical power to various parts of the vehicle.
5. Faulty Hood Switch
Another common reason why a Tucson alarm will go off mysteriously is due to a failed or faulty hood switch.
Also known as a hood latch sensor, this electrical component reports the state of the hood.
When the alarm is armed, the hood should be shut and the switch will confirm this to the car’s computer.
If the hood latch sensor is damaged or broken then this can cause the alarm to go off at random, as it will report an open hood when in actual fact it is closed.
You may also see a warning on the dash such as “Hood Open”.
Hood latch sensors often get dirty and clogged up with grime so it’s worth giving it a thorough clean and some lubrication first.
If you’re a hands-on type of person, you can replace this sensor quite easily with the help of a YouTube tutorial.
If not, have your local mechanic take a look for you.
6. Faulty Door Lock Sensors & Sticking Latches
A faulty door latch sensor is a common cause of Tucson alarms going off. Due to wear and tear and continually opening and closing the door, these sensors can wear out.
Similar to the hood latch sensor, your Tucson alarm monitors the doors to make sure no one is opening them.
Give all door latches a clean and some lubrication with WD-40.
A latch that is sticking can also trigger the alarm.
You will be able to ask your dealer to run a diagnostic test to show the last several reasons why the alarm was triggered.
This can help pinpoint the exact cause, especially if the reports show it was coming from one sensor in one of the doors.
7. Faulty Body Control Module
A Tucson alarm can be triggered by a faulty or damaged body control module.
The body control module or ‘body computer’ is the electronic control unit responsible for monitoring and controlling various systems associated with the vehicle’s body such as the alarm, immobilizers, power windows etc.
The body control module can develop corrosion on the pins or connections can become loose.
Other common symptoms of a bad BCM include:
- Repeated battery drain
- Starting problems
- Erratic electrical functions e.g. horn, wipers, lights, lights on the dash
- Security and alarm system problems
8. Theft Tracker in Vehicle
Many dealerships put a theft tracker in their vehicles. In the event their car gets stolen they’ll be able to track it down.
Although rare, sometimes they accidentally leave these in the vehicle, and this happened to this Tucson owner here.
Here’s what she had to say:
“The dealership left a theft tracker on my vehicle. I took it in and they uninstalled it.”
If you have the Bluelink app you can check this for clues as to why your alarm is going off.
It is best to check the app when the alarm is going off.
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.
Make Sure All Doors Are Shut Properly
This is sometimes overlooked, but make sure all doors, trunk and hood are shut properly.
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 Hyundai Dealership
If needed, take your Tucson 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 car 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 Hyundai’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.
Pull the Horn Fuse
Is your horn the alarm on your security system?
If so, pull the horn fuse.
That should keep it from going off all hours of the day and night.
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.