The Acura MDX is a stylish and versatile luxury midsize SUV.
Like any other car, the MDX’s alarm system may go off at random.
If your MDX alarm keeps going off, continue reading this article.
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Why Does My Acura MDX Alarm Keep Going Off?
An Acura MDX nuisance alarm is most commonly caused by a faulty hood switch. Other causes include faulty door switches, 12V battery issues, key fob issues, not closing doors properly, aftermarket equipment and damaged wiring.
1. Faulty Hood Switch
A faulty hood switch is one of the leading causes of unwanted alarms on the Acura MDX.
The switch is designed to detect whether the hood is open or shut and it 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.
If you’re mechanically inclined you can buy a replacement hood switch online and fit it yourself or the easiest option is to have your dealer take a look.
Here’s what owners on the forum mdxers.org had to say:
“My 2010 MDX’s alarm keeps going off randomly. We have had to keep it unlocked to avoid it happening. It’s at the dealership now and they said it might be the hood latch? They offered two options: $300 parts + 2 hours labor to replace the latch? Or think $100 to turn off the alarm system? What are my options? Looks like the latch is $80 online”
“I just disconnected the hood latch sensor! Fixed my problem right away! Pop the hood, and right under the hood latch there is a connector. Just disconnect that, and your problem is fixed!”
“My 2012 MDX just started doing the phantom alarm this morning. The Service Manager at Acura advised disconnecting the front hood connector. All is quiet again. The front hood sensor is connected to the rear tailgate so the “tailgate open” message will be on your dash even though the tailgate is closed.”
On the acurazine.com forum, one owner posted this recommendation:
“Open your hood and disconnect the latch sensor. Then try to activate your alarm. If it arms you have a faulty switch in the hood latch. Comes free with the purchase of the hood latch. If that doesn’t work try the trunk latch. I’m assuming all door locks work properly. If all else fails, bring it to the dealer. They can see what sensor keeps setting off the alarm.”
2. Malfunctioning Door Switches
Faulty door switches are another common cause of random alarms on the MDX, 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.
But 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.
If you visit your local dealer, they should be able to run diagnostic tests to pinpoint your faulty door switch.
Otherwise, you can try and find it yourself by the process of elimination.
One owner posted on mdxers.org the following:
“About 5 minutes after I lock the truck, the alarm goes off for a few minutes and then goes away after a few more minutes.”
Another owner shared the following advice to diagnose the cause:
- “Try not locking it and seeing if there is no alarm.
- If that’s the case, then sit in the car, make sure the dome light switch is set to “door,” pull the key out of the ignition, and lock it.
- Wait the 5 minutes and see if the courtesy lights come on when the alarm goes off.
- If that happens, then you’ve probably got a door jamb switch problem.
- Sit in the car with all the doors closed and push on the door panels like you’re trying to open the door.
- If any of them trigger the lights and alarm from flexing the door, then you’ve got a bad jamb switch there.”
3. Drained 12V Battery
A faulty or weakened car battery causes a variety of problems, including accidentally triggering the MDX alarm.
The best thing to do is take your MDX 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.
Here’s what one owner on acurazine.com had to say:
“You mentioned the dealership checking the doors. Did they mention checking the battery or other electronic components? Car could be brand new, but the battery may not be. Could be old when installed or even faulty.”
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 MDX.
A bad connection can be caused by dirt or gunk buildup and 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.
- Re-connect the battery, ensuring tight connections
5. Key Fob Issues
A faulty key fob can cause all kinds of issues, including accidentally triggering the vehicle’s alarm.
If it is dirty, damaged or low on battery, the alarm can be triggered at random.
The most common reason is usually a flat key fob battery.
For the sake of a few dollars it’s worth replacing the battery in your fob(s), and it’s also worth spending a bit extra for a good brand of battery.
Whilst you have the fob open to change the battery, give the inside a good clean.
Dirt buildup and dust can cause issues with the electronics.
- 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 swap 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.
6. Not Closing Doors, Hood or Trunk Properly
Sometimes a false alarm can be caused simply by not shutting a door properly, including the hood and trunk.
Here’s one owner’s experience on mdxers.org:
“The problem went away. I think the trunk gate may not have been closed all the way.”
7. Improperly Installed Aftermarket Alarms or Equipment
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.
On the mdxers.org forum, one owner expressed their problems with an aftermarket alarm.
“2010 MDX Base, has factory alarm and aftermarket AutoMate remote start/alarm (installed by prev. owner). Never had an issue with both systems working hand in hand before. Now the alarm randomly goes off in the middle of night, every 1-2 hours. Unplugged hood latch sensor, with no luck. Any other common possible sensors to check before I bring it to a shop?”
8. 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.
9. 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.
Have a look for footprints on the hood and the roof.
Check for Recalls or TSBs
By entering your car’s VIN number on Acura’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 Acura Dealership
If needed, take your Acura 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.