The Toyota Matrix, produced from 2003 to 2013, is a wagon-like compact hatchback.
Like any car, it’s not immune from alarm issues.
If your Matrix’s alarm keeps going off, this article is here to help.
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Why Does My Toyota Matrix Alarm Keep Going Off?
A Toyota Matrix alarm is usually triggered by a faulty hood switch or door switch. Other common causes include battery problems and key fob issues.
1. Malfunctioning Door Switches
Faulty door switches (including the rear hatch) are another common cause of random alarms on the Matrix, 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.
“Oh there is a reason and that is likely one of the door sensors on the door latches inside the door is going haywire and that makes the system think the car is being broken into. Have a scanner hooked up to see what sensor is doing this, they are called door ajar switches.” – FixYa.com
“It was the rear hatch glass, I reopened it and just shut it firmly. It happens every now and then you just gotta make sure the hatch glass is shut completely” r/Toyota
“Found this post trying to diagnose the same issue in my ‘06 Matrix, and just wanted to confirm it was the rear hatch glass (love to know what function it serves to open that) causing the sensor to go off.” r/Toyota
2. Faulty Hood Switch
A faulty hood switch is a common cause of unwanted alarms for Toyota vehicles, including the Matrix 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.
3. Loose or Bad 12V Battery Connections
Loose or bad 12V battery connections can cause a number of problems, including triggering the alarm of your Matrix.
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.
4. Drained 12V Battery
A faulty or weakened car battery causes a variety of problems, including accidentally triggering the Matrix alarm.
The best thing to do is take your Matrix 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.
5. Faulty Key Fob
Another reported cause of nuisance alarms on the Matrix 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 experienced owner on ToyotaNation.com:
“My suspicion is that there’s an issue with the key. The key should not have a transponder in the head of the key. The circuit could have short circuited itself and is grounding when it’s not supposed to. You’ll need to trace the wiring back to the fuse box and verify it’s grounding when the key is turned to run…”
6. Key Fob Running on Low Battery
A common cause of mysterious alarms on the Matrix 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.
7. 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 Matrix’s alarm.
8. 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.
“Most of these aftermarket security systems are stuffed up under the dash on the drivers side and there usually is a rats nest of wires zipped tied up under there also. Check for any valet switches under there or in the plastic left kick panel.” – JustAnswer.com
9. Water Damage
Water leaking into the latches and sensors can occur and cause various issues.
While the quick fix is to dry out the latches and switches with a hairdryer, long term it would be wise to consult with a mechanic to address the cause of the leak.
10. Rust and Corrosion on Door and Hood Latches
Rust and corrosion can also damage the latches and switches, which may trick the sensors into detecting that a door or the front hood is open.
If your car is frequently exposed to moisture or other external elements, then you should routinely inspect critical areas of your vehicle for any sign of rust or corrosion.
11. Damaged Wiring
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.
Due to the soy-based material used for certain cables and wiring, rodents may have chewed through the wires.
12. 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.