The Model S is over a decade old now and it’s still one of the best EVs in the market.
But despite being state-of-the-art, it’s still vulnerable to mysterious alarm problems just like any other vehicle.
If your Tesla Model S’s alarm keeps going off, this article is here to help…
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Why Does My Tesla Model S Alarm Keep Going Off?
A Tesla Model S’s alarm is usually triggered by faulty doors or software issues that cause bugs with the alarm system. Other common causes include trapped bugs, Tesla app issues, and problematic aftermarket accessories.
1. Software Glitches
In some cases, a software glitch or a buggy software update can trigger the alarm at seemingly random times.
Features that were working fine before such as the Sentry Mode and alarm can suddenly start acting strange soon after a software update.
A Model S owner reported an alarm issue after a software update on the TeslaMotorsClub.com forum:
“This seems to happen every month or two. My car is parked in the garage and I’ll approach it to get in. The door handles present, I pull to open the door, and the alarm goes off. Today this happened after cleaning the car. The car also installed a software update last night without issue. I’m not sure if these events are related as I’m not planning for the alarm to go off. This only seems to happen at home, so I’m leaning towards it being software update related, but not sure.”
“Installed another software update today. Opened the car door again as usual, but the alarm didn’t go off this time.”
To clear out any possible glitches, you can try resetting the car’s computers.
To perform a reset, follow these steps:
- Press and hold the two scroll wheels on the steering wheel
- Wait for the screen to turn off
- After a few seconds, the touchscreen should restart on its own
You can do a soft reset even while the car is moving and the car should still drive normally. But it’s always better to do it while safely parked on the side of the road.
Disconnecting the 12-volt battery will also power down the Model S’s computers and force a full restart once the battery terminals are reconnected.
Leaving the car for a while so it can go into a deep sleep state can also clear out software glitches.
If you contact Tesla, they can sometimes manually force a software update to get rid of the problems the previous software version caused.
2. Faulty Doors or Latches
Defective latches and electrical problems with the doors, hood or liftgate can trigger the alarm at random times.
One owner on TeslaMotorsClub.com had alarm issues when their trunk started malfunctioning:
“Looks like Tesla still hasn’t fixed this issue on the refreshed Model S. My 2022 just suffered the same failure. Thankfully the trunk still opens/closes, but the car alarm went off yesterday because it thought someone was trying to open the trunk while it was actually locked and closed.”
“Mobile Service coming tomorrow to replace the Trunk Cinch Actuator part 1003549-00-D.”
Faulty trunk latches are a fairly common issue with the Model S:
“I had similar problem with my trunk unable to latch. It is a 2015 model with manual closing liftgate (not electrical) and a few days ago it was stuck open. The mechanism would not latch even it would close just fine.”
A faulty door handle can also cause issues with the door sensors and make the alarm go off.
Check for any obvious problems like the doors or door handles not operating smoothly or not sitting flush when closed.
Some door issues can also cause error messages to appear on the center screen to help you narrow down the problem.
If all else fails, contact Tesla Service so they can properly troubleshoot and diagnose the issue.
3. Loose Ground Connection
A loose or corroded ground connection can cause a number of seemingly unrelated electrical gremlins including the alarm going off for no reason.
On TeslaMotorsClub.com, one owner had issues with the frunk triggering the alarm:
“This morning, I heard the alarm horn of my Model S honking as I was getting ready to leave my church after the service. The next weird thing was that a message popped up on the screen, saying that the frunk was open. It was only on screen for a few seconds and then disappeared. The frunk looked OK and had not been opened for several days.”
“Just now at home, the alarm actuated again, about 2 hours after the initial event.”
Another owner had similar electrical issues and fixed it by getting a new ground nut installed:
“Look up “corroded ground nut” on the passenger side of the space underneath the frunk – this is a known issue, and I experienced the exact same symptoms. If this turns out to be the cause, any competent indy mechanic can handle this, and some owners have been able to do it themselves.”
“My passenger’s side ground nut was so corroded that it broke off in the mechanic’s hand. He reinstalled a new ground nut somewhere nearby in the space under the frunk.”
Bad ground connections are a fairly common problem with the Model S.
“I have the same issue, frunk open error while driving, low coolant, random alarms, and for the first time the other night the right headlight. No coincidence mine is a 2015 March build as well.”
Some of the common symptoms include:
- Headlight stops working
- “Suspension needs service” error message
- Low coolant warning
- Error messages about the hood being open
- Autopilot won’t work
You can check the condition of the ground wire by opening the hood and removing the frunk tub.
In some cases, you might just need to tighten down the ground nut or remove the corrosion that’s built up on it.
If it’s too rusted out, you’ll need to drill a new hole, tap new threads and install a new stud for the ground strap.
4. Weak 12-volt Battery
A weak 12-volt battery can cause a lot of strange electrical issues in the Model S, including more frequent false alarms.
The Model S’s infotainment and a lot of its computer systems run off the 12-volt battery.
Sentry Mode and leaving a key fob in range can also keep the car awake and drain the battery much quicker.
Normally, this gets charged by the large EV battery every time you drive.
If you let the Model S sit for several days or if the car’s 12-volt battery is already 3 or more years old, it might be too weak to hold a charge.
Batteries can also wear out within a year due to manufacturing defects.
If you suspect the 12-volt battery is dying, you can have it tested at an auto parts store, or just simply spring for a new one.
5. Bugs Inside the Cabin
Aside from software bugs the Model S alarm can also be triggered by actual insects or tiny critters getting stuck inside and triggering the interior sensors.
It may sound unlikely, but it’s one of the more common causes of false positives.
One owner on the TeslaMotorsClub.com forum had this to say:
“I am still wrestling with the problem of small flying insects (unseen when I park) triggering the EATS when the car is otherwise undisturbed.”
EATS is Tesla’s optional Enhanced Anti-Theft System which adds a sensor to detect motion inside the cabin.
To get rid of any insects inside the car, try the following:
- Leave the doors and windows open for a while
- Vacuum inside the car
- Use bug repellent or bug traps
To check whether something inside the car might be triggering the alarm, you can turn off the Tilt/Intrusion sensor temporarily.
This setting can be accessed by going to Controls and then selecting Safety.
In some cases, an expanding plastic water bottle when the car is parked in the sun can also cause the alarm to go off.
Checking Sentry Mode events will also sometimes let you know what caused the alarm to go off. If all else fails, Tesla service can check which sensor is triggering the alarm.
If you need to leave the car with passengers or pets inside, you can turn on Dog or Camp mode. If the car is being transported, you can also put it into Transport mode to keep the alarm from going off.
6. Sentry Mode Issues
When the Sentry Mode cameras detect motion around the car, it can cause the alarm to go off.
Sometimes, even harmless things moving around the car can create false positives such as:
- Flickering lights
- Leaves or branches
- Strong vibrations
- Other vehicles
If you’re parked out in public, false alarms are more likely to happen.
Loud noises that create strong vibrations such as rumbling engines, construction work or thunderstorms can also trigger Sentry Mode to start recording and eventually set off the alarm.
A few owners on the r/TeslaLounge subreddit shared their experience:
“I found out that loud engines set off Sentry Mode. The two times it was triggered on my cars have been to a loud engine starting or driving by.”
“A loud unmuffled ICE vehicle could set it off. my alarm has been triggered in the past by a thunderstorm.”
“I’ve had multiple false alarms with Sentry Mode in parking garages.”
If you receive a notification on your phone saying “Sentry Mode has triggered the alarm state” this means your alarm has gone off.
You can always check the live footage on the app to see if there’s anything suspicious going on with your car when you see these notifications.
If Sentry Mode is always triggering the alarm even if you’re parked in a secure location such as your garage or driveway, you can always just turn it off until you find out the root of the problem.
You can also turn off the cameras by toggling Camera-Based Detection in the Sentry Mode settings.
Even with cameras off, Sentry Mode will still record footage and the alarm will still go off if the tilt and intrusion sensors are triggered, like when someone accidentally bumps into the car while it’s parked.
If all else fails, try removing the USB drive you use for Sentry Mode as some drives can cause random issues.
If you want to keep the alarm from going off but still want Sentry Mode, you can choose Disable Sentry Sounds under the Controls and Safety settings.
7. Vibrations from A/C compressor or Fans
The Model S’s A/C compressor and fans can create enough vibration to trigger the alarm.
Turning on the A/C remotely using the app, for example, can sometimes make the alarm go off.
The Cabin Overheat Protection, which automatically turns on the A/C to cool down the cabin, is another common culprit.
One owner posted their experience on TeslaMotorsClub.com:
“Every time when it’s hot outside and I want to turn on the air conditioning from the app to cool the car down, it triggers the sentry alarm. 3 times I’ve tried this now, and each time the alarm goes along with the loud music from the car.”
Preconditioning to warm up the cabin and high-voltage battery during the winter can also trip the alarm.
Another Tesla owner described their alarm issues on the r/TeslaMotors subreddit:
“Happened to me when I tried preconditioning the AC. Sentry alarm went off.”
To eliminate this as the possible cause, turn off Cabin Overheat Protection and Preconditioning, then observe if the alarm sounds off again.
You can also disable the Tilt and Intrusion sensors by going to the Controls and then Safety settings.
8. Opening a Locked Door from Inside
If the doors are locked and one of the doors or the liftgate is opened, the alarm will be triggered.
This was designed so that the alarm goes off in case someone breaks your window and tries to open the door by reaching inside.
But this also means that if you walk away with the key fob and leave someone in the car, the alarm will go off if they try to get out.
Here’s what one owner on the TeslaMotorsClub.com forum had to say:
“So apparently, if the doors are locked, you need to either unlock them with your phone, or tap the button once to wake up the electronics, and then unlock with the screen.”
The interior door button and emergency release will always open the doors even if they’re locked so that people inside can still easily get out in case of an accident.
If you want to make sure the alarms don’t go off, here are a couple of things you can do:
- Unlock the car first using the app or through the main screen before getting out
- Lock the doors using the main screen, not the app or key fob
- Enable Dog or Camp mode
- Turn the alarm completely off on the main screen
- Keep the key fob inside the car
- Turn off the Walk Away Lock feature
9. Aftermarket Accessories
Issues and glitches with accessories like USB devices, dash cams, lights or aftermarket frunk openers can cause the Model S’s alarm to go off at random.
Unplug all the non-stock parts from the car and observe if the alarm is still triggering on its own.
If you suspect that your USB drive is causing an issue with the alarm, try another storage device or reformat your current one.
10. Tesla App Issues
The Tesla app on your phone can sometimes run into glitches and cause random issues with the alarm.
On TeslaMotorsClub.com, one owner had the alarm go off every time they opened the app:
“It’s definitely the app setting the alarm off when I open it on my phone. Tested twice and alarm went off twice.”
“It happened again two nights ago. I deleted my wife’s phone from the car and boom, hasn’t happened since.”
To fix these software bugs, try the following:
- Toggle your phone’s Bluetooth on and off
- Restart your phone
- Make sure the Location settings for the app is set to Always
- Reinstall the Tesla app
- Remove the phone by going to the Controls and then Locks setting
You can also toggle the Walk Away Door Lock feature and manually lock the car instead using your phone or key fob.
If you have the Exclude Home feature enabled for the locks, make sure your saved locations are correct.
11. Weak Key Fob Battery
A weak key fob battery can cause issues with how the car’s locks and alarms work.
You can always try replacing the key fob battery even if they’re just a year or so old since they’re very cheap anyway.
The installed battery may have been defective from the factory or an old one that’s been kept in stock for too long.
To replace the Model S’s key fob battery, follow these steps:
- Pry open the battery cover using a small flathead screwdriver or similar tool
- Remove the old battery
- Wipe the insides of the key fob even if it’s fairly clean
- Insert the new battery with the flat side facing towards you
- Reinstall the battery cover
12. Key Fob Issues
A faulty key fob could be the main culprit of your Model S’s alarm problems.
Sometimes, simply placing the key fob next to something that could interfere with its signal like your phone can cause it to act up.
You can also unpair the key fob from the car temporarily and see if that fixes the alarm issues.
While you’re observing the problem, you can use your phone or key card to unlock and drive the car.
If you’ve narrowed down the issue to the key fob and you’ve already replaced the battery, you can get a new one through the Tesla online shop.
Check for Recalls or TSBs
Check for recalls for your vehicle by going to the NHTSA or Tesla Service recall page to see if there are any outstanding issues with your car that may affect the alarm system.
Entering your VIN on the NHTSA website’s Safety Issues and Recalls page will also show you a list of TSBs (Technical Service Bulletin) for your specific vehicle. Look out for any known problems with the doors, electronics or software that may be related to your alarm issues.
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.
Check the Wiring
Loose electrical connectors and broken wiring harnesses can cause mysterious alarm problems.
Wiring issues are more common in the following scenarios:
- After having the car repaired
- If the car has been damaged due to an accident
- Previous incidents of water intrusion
- Corrosion due to age or lack of maintenance
Check the 12-volt battery terminals and make sure they are properly bolted down. If you see any debris or corrosion on the terminals, clean them out first.
You can also check any exposed wiring for any obvious signs of damage or wear.
Check the Car’s Logs
Aside from asking Tesla Service, you can check your car’s logs yourself by using third party apps like TeslaFi or TeslaMate.
This should give you a more detailed view of what’s happening whenever the alarm is triggered.
Schedule a Service Appointment
If you’ve run out of ideas trying to troubleshoot the problem on your own, you can schedule a service appointment through the Tesla app.
You can either take it to the nearest Tesla service center or have a mobile tech come out to your location.
Once you schedule an appointment, you can start talking to a representative about your problem.
If you’re able to resolve your issue after consulting with a representative, you won’t be charged for the service as long as you cancel the appointment at least 24 hours in advance.
How to Test the 12V Battery
How to Test the Battery:
- Before testing, remove the surface charge from the battery, this allows for an accurate reading.
- Power down the car and leave it unplugged for several hours
- 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.