Updated at: 22-08-2022 - By: Lucas

When it comes to deterring criminals and informing owners when someone tries to mess with their car, car alarms are an excellent choice. It can be an annoyance and a nuisance if your auto alarm goes off for no apparent reason. The likelihood is that if you own a car, at some point in the past your alarm has sounded without you understanding why.

Car alarms are intended to keep criminals out of your vehicle, so why does one sound as you turn the key to unlock the door?

Here, we’ll go over the various reasons why your car alarm goes off when you unlock it with a key. It’s a common problem, but it’s easy to correct.

Why Does My Car Alarm Go Off When Unlocking With a Key?

Car Alarm Goes Off When Unlocking With Key

The loud noise that car alarms make serves as a theft deterrent, alerting the owner of the vehicle that an attempted theft has occurred. However, your car alarm may sound even if no one has attempted to get into your vehicle in a long time..

There are many parts to modern automobile alarms. an array of sensors, a loudspeaker, and a receiver tuned to your keycode are all included in this system. Your car alarm is activated when a reaction is received by one or more sensors, which can be caused by the car moving when the engine is off, a loud noise, or something landing on or near the car.

Until it is reset or turned off, the automobile alarm will ring every time a sensor responds. Your car’s alarm is always ringing, but it will become silent if there is no suspicious activity.

5 Reasons and Solutions


There are several reasons why your car alarm will sound when you unlock it with a key. Car alarms might go off for a variety of reasons when a key is used to unlock the door.

1. Sensitive Sensors

When a sound or movement is detected by the auto alarm’s sensors, the alarm goes off. For example, if you try to unlock your car by inserting the key in the lock, your car’s sensors may be activated.

Car alarm sensors might be activated by the sound of a dog howling nearby or even just by someone leaning against your vehicle!


Oversensitive car alarm sensors don’t necessitate a trip to the shop. Locate the alarm in your vehicle’s manual and follow the instructions within to re-calibrate your sensors. Your auto alarm sensors will be less sensitive and won’t be triggered by just trying to unlock the door once you’ve correctly altered them.

2. Broken Remote Key

When you unlock your car with a malfunctioning key fob (or remote key), it may set off your car alarm. In most cases, pressing the unlock button on the remote will turn off the alarm system. If, however, the remote is malfunctioning or the battery is dead, the alarm may remain on and sound when you open your car door.


Your key fob’s battery may be all that’s needed to remedy this problem. If the issue persists, the key fob may have to be reset or reconfigured from scratch.

3. Locked The Car Using Key Fob

It is engaged when you use the remote key fob to lock your automobile. Your car alarm will sound if a door is opened with a key in the lock and not by pressing a button on the key fob, which is what the dome light circuit does.

As a result, your automobile doesn’t know if it’s been opened by your key or someone else picking the lock. An alarm will sound when the door is unlocked without the car getting a signal from its key fob, which is why it is so important to keep your car’s ignition key in the ignition at all times.


If you used your key fob to lock your car, you should always use it to unlock your car. You can, however, use the ignition to turn off the car’s alarm if you accidently set it off while unlocking the door with the key in the door. The automobile alarm will be deactivated as soon as the key is recognized by the vehicle.

4. Car Battery Needs Charging

When you try to unlock your car with a key and your alarm goes off at odd times, it’s possible that your battery is low or damaged, which would explain the problem. Because the auto alarm is powered by the vehicle’s battery, a problem with the battery could lead to problems with the alarm.

In addition, if the terminals of your car battery are rusted or the battery is corroding, the alarm system may sound. If your car alarm keeps going off ‘for no reason,’ you should look into the health of your vehicle’s battery.


A voltmeter can be used to assess the level of charge in your car’s battery. You’ll have to recharge your automobile battery if it’s not getting adequate voltage. Use a battery cleaner if you need to clean the battery, but make sure you wear appropriate clothes.

The battery in your automobile may need to be replaced if it is severely corroded and damaged. Using a key to open your vehicle should stop your auto alarm from sounding anymore if you have a functioning battery.

5. Panic Button Was Activated

If you’ve mistakenly pressed the panic button on your key fob while unlocking your car, the alarm may go off. A panic button on a key fob makes it easy for drivers to activate their vehicle’s alarm without reaching for their keys (usually orange or yellow). However, it can be a nuisance when you activate it while trying to unlock your car, especially if you detect someone suspicious approaching your vehicle.


Fortunately, this is a simple issue to fix. Just hit it again if you mistakenly activate your panic button. You can silence the car’s alarm by starting the engine and putting the key in the ignition.

FAQsCar Alarm Goes Off When Unlocking With Key-2

Why Does My Car Alarm Keep Going off in the Middle of Night?

Your battery may be running low if your car alarm continues going off in the wee hours of the night. If you leave your car parked overnight and your battery is low, your car alarm may go off since the battery is powering it.

An issue with the hood latch sensor or a door lock sensor could be the cause of your car alarm system not working properly, or the whole system could have been placed incorrectly. It’s possible that nocturnal animals are to blame if your car’s sensors are overly sensitive.

Why Does My Car Alarm Keep Going off Randomly?

Your auto alarm may be going off at random for a variety of reasons. An overly sensitive auto alarm may be causing your vehicle to sound an alarm based on sounds and movements that are too close to your vehicle. There could be a problem with your car battery or with the installation of your auto alarm system.


While car alarms might be essential in protecting your vehicle from thieves, they can also be a nuisance when you’re merely trying to get into your vehicle with the key. If your car’s alarm sounds when you open it with your key, don’t freak out, there are numerous reasons for this and they can all be repaired with a simple phone call.

To help you understand why your car alarm goes off when you unlock it with a key, here are the five most typical causes. So, if your car alarm goes off while you are trying to unlock the door, you now know what to do.