Car Alarm Goes Off When Unlocking With Key - 6 Top Causes - Car Super Care (2022)

Quick Navigation

    • 1. Set The Car’s Alarm Using The Key Fob
      • How To Fix It
    • 2. Overly Sensitive Shock Sensors
      • How To Fix It
    • 3. A Broken Microswitch
      • How To Fix It
    • 4. A Faulty Key Fob
      • How To Fix It
    • 5. Accidental Alarm
      • How To Fix It
    • 6. Low Battery /corroded Battery
      • How To Fix It
  • Bottom Line

Car Alarm Goes Off When Unlocking With Key - 6 Top Causes - Car Super Care (1)

I have been a driver for many years, and I have faced many car problems over that period. However, one of the most irritating car problems I have encountered is the car alarm going off. Whether I am in the house relaxing or in a traffic jam, the noise caused by the alarm is nerve-wracking.

In most of those cases, the car alarm went off because of a loud bang. Recently, my car alarm has been going off when unlocking using a key. After doing some research and finding out the reasons, I decided to share my results with you in this post.

So, if you ever come across a car with an alarm that goes off when unlocking using a key, here are the reasons why. Also, we’ll talk about how to fix them. So, get ready!

1. Set The Car’s Alarm Using The Key Fob

The first suspect should be your car security system. If you lock your vehicle using the key fob, you will have to unlock it using the same key fob. If you use a key to open it, the car will sound off the alarm.

This is a security measure as the security system will think that someone is trying to break in. Thanks to the dome light circuit that alerts you if the door is opened.

(Video) Use Key to unlock car, no alarm sounding

The key fob is specifically coded to the car and transfers an encrypted signal to open the car’s door. If you use the car key to open, this signal will not be detected; thus, the alarm will turn on. If you use the key fob to lock the car, unlock it using the key fob to avoid sounding the alarm off.

How To Fix It

Nonetheless, this issue can be fixed in a few easy steps. After you open the car using a key instead of a key fob, you can still stop the alarm. All you need to do is to place the key in the ignition and turn it.

Since the key has a Radio Frequency Identification (RFID) chip, the car will read it and confirm that the key is legitimate, which will automatically deactivate the alarm.

2. Overly Sensitive Shock Sensors

Another reason why your car alarm may go off when unlocking is because of overly sensitive shock sensors. Most aftermarket alarms work by sensing vibrations or shock sensors. Hence, these can sense when another car passes by or even a slight sound of a barking dog.

But if the shock sensors are extremely sensitive, then a simple touch as you attempt to open the car’s door may trigger the alarm. Also, when a goat or dog leans on your vehicle, this may sound off the alarm.

How To Fix It

Fixing a shock sensor is a simple DIY task. All you have to do is go through your user manual to locate the sensor. Then, configure the sensor by simply twisting it. Follow the instructions to the end to avoid making any mistake.

3. A Broken Microswitch

If your vehicle’s microswitch is broken, then your car alarm will be turned on every time you open the door. Note that every vehicle’s door is fitted with a lock cylinder. This is the system in charge of locking and unlocking car doors.

A microswitch is located on the back of every lock cylinder. On top of that, the microswitch is wired to the body control module. Additionally, it tells the body control module when you enter the car and alerts it to disarm the alarm.

(Video) Car Alarm Keeps Going Off - How To Fix It

So, if you unlock the driver’s side door and the alarm turns on, this is a sign that you have a broken microswitch.

How To Fix It

Fixing the broken microswitch is quite challenging as you have to remove the door panel. However, a technician or mechanic will have an easy time repairing the microswitch. So, it’s better if you have the mechanic fix the microswitch.

Car Alarm Goes Off When Unlocking With Key - 6 Top Causes - Car Super Care (2)

4. A Faulty Key Fob

If your key fob is faulty, this can also cause the car alarm to go off. You don’t need to press the key fob for it to sound off the alarm. This small gadget can send a signal just like that. A key fob is a device that locks and unlocks your vehicle. It is also referred to as the remote key.

How To Fix It

The good news is that it can be fixed quickly and straightforward. Start by replacing the key fob batteries. If it doesn’t work, reset the gadget to restore its normal performance. If need be, you may have to reconfigure the device.

5. Accidental Alarm

Perhaps you accidentally turned on the key fob in your pocket while opening your car using the key. The key fob has a panic button that can turn on the alarm if you press it accidentally. Most key fobs have a yellow or orange panic button.

How To Fix It

If you accidentally turned on the alarm sound, you can turn it off using the panic button. Alternatively, you may also turn off the panic button by starting and driving the car.

6. Low Battery /corroded Battery

It may be a sign that your car battery is running low. Car alarms are designed to alert the driver of a low battery. If you attempt to unlock your car using keys and the alarm turns on, this should be a sign that the battery is not low but dying.

(Video) Doing This Will Reset Your Car and Fix It for Free

Therefore, you should recharge your car battery as soon as possible.

If your battery is not low, then it may indicate that your battery is corroded. If it has rusty or worn-out terminals, the alarm will sound off. If not corrected, this may make the car’s electrical system to fail, with the alarm system included.

This is because your car’s electrical system may be confused and misinterpret the battery to have a low charge, which will also turn on your car alarm.

How To Fix It

Use a voltmeter to find out if the battery is low. If that’s the case, you can go ahead and recharge the battery. But if it’s the corrosion causing the car alarm to come on, you should clean the battery terminals using a battery cleaner. Remove the terminals and wear protective gear before cleaning.

See Also:Best 6 Terminal Removal Tool Kits (Review)

Bottom Line

If your car alarm goes off when you unlock it using a key, there is nothing to panic about. After looking at the possible causes and how to fix your car alarm, you should handle the issue fast.

But if you’re unsure what’s causing the car alarm to go off, you can take the car to a mechanic. You can go ahead and drive your vehicle peacefully without the annoying alarm sound.

Car Alarm Goes Off When Unlocking With Key - 6 Top Causes - Car Super Care (3)

With comprehensive experience in writing exceptional quality articles and blogs about cars and related stuff, Daniel is one of the finest bloggers and a hardcore car lover we have. He is an ASE certified technician with an across-the-board experience of 10 years in the industry. He could not help tinkering with anything he got his hands on from a young age, which led to his remarkable career in the automotive repair industry.

When he is not under any hood, you can find him on the water or in the woods to pursue his passion for hunting and fishing. He has been writing for multiple sectors and is a regular contributor to several publications.

He currently owns a Nissan 300ZX TT and a Pearl Yellow but plans to upgrade it to 550 HP. His favorites include the Koenigsegg CCX and Lamborghini Diablo 6.0 VT, but for him, the Ferrari 360 Spider is one of the sexiest cars that exists to date.

Being an avid world traveler, he has spent most of his time analyzing the automotive markets, latest technology, and local favorites to enhance his knowledge base. He is currently living in North Caroline, where it’s all about food and coffee and, of course, cars.

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Why does my car alarm go off when I unlock with the key? ›

When you lock your car using the remote key fob, the car's security system is activated. The dome light circuit alerts your car alarm when a door has been opened, if your door is opened with a key in the lock and not by pressing a button on the key fob, your alarm will be triggered.

How do you open a car door without the alarm going off? ›

Use Key to unlock car, no alarm sounding - YouTube

Can a car alarm go off while unlocked? ›

Many car alarms will shut down when the car doors are unlocked by the keys or appropriate key fob. If the door locks do not respond, the batteries may be dead in the key fob. Replace the batteries and try again.

How do I reset my car alarm system? ›

Car alarms rely on the electronic component of the vehicle, and disconnecting the battery should both silence the siren and reset your alarm. Open up the hood, locate the battery, and with a wrench, remove the negative terminal. Then reconnect it after a minute has passed.

Can bad battery cause alarm to go off? ›

If your car alarm goes off in the middle of the night and your car battery is dead the following morning, then the car battery is likely the main culprit. One of the main functions of a car alarm is to warn the driver about low battery levels.

How do I get my car out of anti theft mode? ›

Look for a button that allows you to slide the physical key out of the fob. Step 2: Turn the vehicle key to unlock the car door without releasing it. Hold the key for 30 seconds in this position. This will signal to your car's system that you have the right key, and will enable you to bypass your car's alarm system.

How do I deactivate my alarm system? ›

You can turn off or power down your home alarm system by disconnecting its backup battery and then unplugging the transformer for the device from the wall outlet. You can confirm that the panel has been powered down by checking its touchscreen or keypad and making sure that it is blank.

What triggers a car alarm? ›

Answer provided by. Most car alarm systems are triggered by shock or vibration sensors. These sensors will detect when something is moving the car, like a potential thief or your unsuspecting dog. The movement is what triggers the alarm.

Do car alarms eventually stop? ›

Car alarms stop on their own if they have a built-in timer. Alarms of some older vehicles did not have a timer and would go off for days until the battery was dead or the alarm was switched off. New alarm systems usually go off for 15-30 second intervals over a time period of 20 minutes.

How do you turn off a car alarm with a key fob? ›

Quick fixes. In most vehicles, you can silence the alarm system by pressing the lock and unlock button on the key fob. Another common remedy is to manually unlock the driver's side door with the key. If these two options don't work, insert the key into the ignition and try starting the vehicle.

How do I know if my car is in anti theft mode? ›

If the security or anti-theft light is flashing when you attempt to start your car, and the engine does not crank or does not start, you have an anti-theft problem. The system may not be recognizing your key or keyless entry signal, or there may be a fault in the anti-theft module, keyless entry system or wiring.

What causes car alarm to go off randomly? ›

What is causing a car alarm to keep going off randomly? The most common reason why a car alarm keeps going off is a low battery charge or an incorrectly set movement sensor. It can also be caused by a faulty hood latch sensor, door lock sensor, faulty key fob, or an incorrectly installed car alarm.

How do you unlock your car when your keys are inside? ›

Here are a few tips to safely get inside your locked car.
  1. Get Your Spare Key. ...
  2. Load Up Your App. ...
  3. Unlock Manual Locks with String or Fishing Line. ...
  4. Unlock with a Wire Clothes Hanger. ...
  5. Unlock with an Inflatable Pump Wedge. ...
  6. Unlock with a Strip of Sturdy Plastic. ...
  7. Call AAA or a Locksmith. ...
  8. Call the Police.
May 6, 2021

How do I unlock my car door from the outside? ›

How to unlock a car door (without a key) - YouTube

How do I stop my dog from setting off my car alarm? ›

watch the center screen when you turn the car off - there should be a prompt to turn off the motion sensors. Or you can just go into the settings and turn off the motions sensors so it won't ask each time.


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