The Toyota Tundra, introduced as a 2000 model year, is a full-size truck with impeccable towing and hauling capabilities.
Like almost any other truck, the alarm can be tripped unintentionally.
If your Tundra’s alarm keeps going off, this article covers the most common causes and solutions.
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Why Does My Toyota Tundra Alarm Keep Going Off?
A Toyota Tundra alarm is usually triggered by a faulty hood or door switch. Other common causes include 12V battery problems, leaving the dome light on, a low key fob battery, accidentally pressing the key fob’s panic button or an incorrectly installed aftermarket alarm.
1. Faulty Hood Switch
A faulty hood switch is a common cause of unwanted alarms for Toyota vehicles (Tundra included).
The switch is typically embedded in the hood latch.
The small electronic device is designed to detect whether the hood is open or shut and is an important part of the car’s alarm system – if it is broken, loose or dirty it can send false readings to the car’s computer thus triggering the alarm.
- Pop the hood and locate the hood switch.
- Check for any obvious damage, rust or loose connections.
- Give the hood switch a clean too (use contact cleaner), as dirt and grime can cause issues.
- You can test the switch with a continuity tester.
If you are well-versed mechanically, you can buy a new hood switch online and replace it yourself. Otherwise, we’d advise visiting your local mechanic.
“Good chance it’s the hood latch sensor. I had the same symptom on my 2016 and changed it out and have not had a problem. Mine was doing it mostly on cold nights. I suspect that the change in temp as the truck cooled down was causing the switch to malfunction.” – Tundras.com
“Would test the switch under the hood to make sure it is working…” – TundraSolutions.com
2. Malfunctioning Door Switches
Faulty door switches (including the rear hatch) are another common cause of random alarms on the Tundra, similar to the hood switch, these switches monitor the open/closed status of the door – if damaged, faulty or dirty they can send false readings thereby triggering the alarm.
Door switches are a common point of failure as they are subject to wear and tear due to the doors being continually opened/closed/slammed etc.
The door latches and door switches can get dirty too which can cause issues, so the first thing you should do is give all door latches a good clean and spray some WD-40 on the latch and work it in to see if that helps.
Also check the wiring leading from the body into the door for any signs of damage, it should be in a flexible hose on the hinge side of the door.
If you suspect the alarm issues are linked to the door switch, ask your dealer to run a diagnostic test to try and pinpoint the fault.
3 Leaving Dome Light On
For some models and variants, leaving your interior lights (or dome lights) on may cause the alarm to go off, this is so that you don’t drain the 12V battery.
Before leaving your vehicle, make sure that all electronics are properly shut down or toggled off.
“Had this happen when I first got the truck. Pissed me off because I couldn’t figure it out. Had to disconnect the battery overnight. Went to work the next morning and realized I left the dome light on. I didn’t think that could be it but it sure as hell was…” – Tundras.com
“Ta-Da. Dome light was on… damn kids. Still daylight here so I didn’t even notice. Thanks brotha!! Simple fix, but really appreciate it.” – Tundras.com
4. Loose or Bad 12V Battery Connections
Loose or bad 12V battery connections can cause a number of problems, including triggering the alarm of your Tundra.
A bad connection can be caused by dirt or gunk buildup.
The terminals may have come loose from driving and vibrations etc.
Make sure the engine is off before doing any work on the battery.
- Inspect the battery and look for any signs of damage, dirt build-up, rust, or corrosion.
- Disconnect the battery and loosen the nuts on the clamps using a wrench.
- Remove the negative clamp, marked with a “-” first.
- Clean the terminals with a toothbrush dipped in a mix of baking soda and water, rinse with distilled water and dry with a cloth.
Reconnect the battery, ensuring tight connections.
5. Drained 12V Battery
A faulty or weakened car battery causes a variety of problems, including accidentally triggering the Tundra alarm.
The best thing to do is take your Tundra for a battery health check, these are usually quite inexpensive or sometimes free such as at AutoZone.
Or you can test it yourself with a multimeter (see the guide at the end of this article).
A healthy 12V battery should be about 12.6 to 12.8 volts while a weakened battery reads below 12 volts.
“Check battery voltage and connections.” – TundraTalk.net
“Some alarms will false trigger when the remote batteries need replacement.” – TundraSolutions.com
“The problem was a weak battery. In colder weather the voltage drop is similar enough to break so that the alarm trips the same way it would if a door was opened and the light came on…” – ToyotaNation.com
6. Accidentally Triggering the Key Fob’s Panic Button
It is not uncommon for owners to unintentionally activate the panic alarm of their vehicle.
While a lot of owners have chalked it up to poor key fob design, a few others have attributed unintentional triggering to other objects in the same pocket as the key fob.
“This same kinda thing has happened to me. I have noticed though that the Key fob is very delicate while in your pocket. If I turn the wrong way or lift my leg or sit down a certain way it has thrown off the alarm. Not sure but, it is annoying when it happens.” – Tundras.com
“The Toyota key fob is poorly designed such that buttons are pushed simply by pressure of your cloth pants pocket against the surface of the fob. I’ve had the doors lock by bending down with my keys in my pocket.” – Tundras.com
7. Faulty Key Fob
Another reported cause of nuisance alarms on the Tundra is a faulty key fob.
If you have 2 remotes, try taking the battery out of one and use the other for a while.
If the alarm problems persist, and you have tried cleaning the inside of the fob(s) and changing the battery, the best thing to do is speak with your dealer.
We found this post by an owner on Tundras.com:
“Most likely it’s an issue with the remote start. Either the module or programming isn’t up to date to work with the 18+ ecu. Easiest thing is to simply unplug the module for the remote start and see if it stops.”
8. Key Fob Running on Low Battery
A common cause of mysterious alarms on the Tundra is a low key fob battery. Similarly, if the fob is dirty or dusty this can also cause alarm issues.
Give the inside of your fob a clean and replace the battery to eliminate this possible cause. It’s worth spending a bit extra for a good brand of battery.
- To open your key fob, stick your prying tool into the slit or gap between the two halves of the outer casing and gently apply upward pressure to pop open the device.
- Remove the battery.
- Give the key fob a good clean to remove any dirt or fluff – a cotton swab and some rubbing alcohol should do the trick.
- Check for damage, rust or loose connection (you may need a new key fob depending on what you find).
- Be sure to insert the new battery facing the right way up.
- Assemble the outer casing of your key fob by clamping them back together.
“Try changing the fob battery.” – TundraTalk.net
9. Incorrectly Installed Aftermarket Alarm
An incorrectly installed or faulty aftermarket alarm system is a common cause of nuisance alarms.
Aftermarket alarms are typically far more complex than any factory-installed equipment which makes them more prone to issues.
They may also have been installed by incompetent individuals.
If you are experiencing issues with an aftermarket alarm, the best thing to do is speak with a reputable auto electrician.
10. Damaged Wiring or Electrics
Damaged electrical wiring can cause a wide range of problems, it can often be tricky to pinpoint too and you may need to have an auto electrician run some diagnostic tests.
There may also be some kind of electrical malfunction due to water damage, so its a good idea to inspect your vehicle for any obvious signs – especially near the BCM.
“Could be a bad/shorted connection or corrosion somewhere.” – Tundras.com
Due to the soy-based material used for certain cables and wiring, rodents often chew through them. Inspect your Tundra for any obvious signs of rodents and inspect the wiring, you may need to have your dealer take a closer look.
11. Opening the Vehicle Without the Key Fob
For some models and variants, if you leave your vehicle after powering it down, the alarm system is automatically armed after 30 seconds, regardless of whether you locked it or not.
If you find yourself tripping the alarm system after attempting to open any door or hood 30 seconds after turning off your vehicle, then make sure to unlock the vehicle with your key fob first to disarm the alarm.
“That’s what it is supposed to do when you set them to arm automatically. It sets the alarm after the doors are closed for 30 seconds without the key in the ignition. If you open them without the key fob the alarm goes off.” – TundraTalk.net
“Lock your doors and close it, wait till the alarm resets and then unlock the door with the key and this should take care of your problem.” – FixYa.com
12. Not Closing Doors, Hood, or Trunk Properly
Something as simple as not properly closing the doors, hood, or trunk will inevitably trigger the alarm.
Make sure to check if you have closed every point of entry of your vehicle to avoid accidentally tripping your Tundra’s alarm.
13. Faulty Body Control Module (BCM)
A faulty body control module can cause a wide range of issues including nuisance alarms.
- The BCM is in charge of electrical communication from different electronic systems.
- This includes the car alarm system, lock-unlock functions, climate control etc.
If you feel that your BCM is the culprit behind random alarm activation, then book an appointment with your local dealership to have it inspected.
14. Animals Climbing On The Vehicle
If your alarm has been set off in the middle of the night, it may have been by an animal climbing on the car.
States such as Illinois, Indiana, Iowa, Texas, Wisconsin, and Carolina have large wild raccoon populations.
- Have a look for footprints on the hood and the roof.
- If you have a CCTV system, examine the footage. These animals usually appear during the night.
Check for Recalls or TSBs
By entering your car’s VIN number on Toyota’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.
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 Toyota Dealership
If needed, take your Toyota 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 your unit is still under warranty then they should fix and resolve the issue for free.
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.
- 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.