When working properly, alarms are perfect for preventing criminals from stealing vehicles. When they have problems, they can create some embarrassment instead. If the car alarm has "gone mad", you can try several methods to shut it down or reset the on-board computer that controls it. Start with the quickest, simplest remedies you have, and then move on to more complex ones if the need arises.
Steps
Method 1 of 3: Use the Keys or the Remote Control Keychain
Step 1. Use the car key to lock and unlock the driver's door
Many original alarms are designed to go off when they perceive the key or key fob with remote control nearby. Some models can be deactivated by inserting the key into the driver's door lock to lock and unlock it. Since the car is unlocked with the correct key, it may send the shutdown signal to the alarm.
- While this method can also be applied to the passenger side door, it is much more likely to be effective on the driver's door.
- If the door is already closed, simply open it; if you don't get results, try closing it and reopening it again.
Step 2. Use the remote control key fob to lock and unlock the car
Following a similar methodology to that described in the previous step, it is useful to open the door lock using the central locking remote control to disable many factory alarms. When you are close enough to the car for the remote to reach the sensor, press the button to close the locks followed by the button to open them. Many alarm systems shut down in this manner.
- If the locks do not respond, the remote control batteries may be dead; replace them and try again.
- If the doors open but you are unable to turn off the alarm siren, professional repair may be required.
Step 3. Check if you have touched the emergency button
Some remote controls are equipped with a "panic" button which activates a function very similar to that of the alarm. A siren starts to sound and the headlights turn on and off; if you pressed it by mistake, the function will not deactivate until you select the key again. In some cases, you can turn it off by starting the car and starting to drive.
- Most emergency systems deactivate after a certain period of time.
- The panic alarm may not go off when you start the engine, but when you start driving.
Step 4. Start the machine
The alarm has been designed to prevent the theft of the vehicle by a person who does not have the key; therefore, starting the engine correctly is often sufficient to resolve the situation. Open the door and enter the passenger compartment, insert the key and turn it to the "ACC" position (accessories). If that doesn't work, try starting the engine. Remember that some non-genuine anti-theft systems may prevent you from turning on the car while they are running, even if you use the key.
By turning the key in the ignition you should be able to turn off the siren, but that's not always the case
Step 5. Consult the use and maintenance manual
Staying near a car with the alarm siren ringing is certainly not the most relaxing time to read something, but the car's manual can provide you with some important information to deactivate it. If you are unable to turn off the system with the key or remote control, check the user manual to understand how to proceed.
- Each car manufacturer uses different alarm systems; it may therefore be necessary to take specific actions to be able to deactivate yours.
- You may have to repeat a certain action a certain number of times to reset the on-board computer, such as closing and opening the locks.
Method 2 of 3: Remove the Anti-theft Fuse
Step 1. Locate the correct fuse box
Most modern automobiles have more than one, distributed throughout the vehicle and managing the various electronic components. Consult the use and maintenance manual to identify the one that contains the factory alarm system fuses. The box could be in the engine compartment or in the passenger compartment; in the latter case, it may be necessary to remove some dashboard moldings to gain access.
- Be careful when disassembling the plastic components from the interior, as they are fragile and tend to break.
- Store these items aside so they are out of the way and to avoid stepping on them or sitting on them while you work.
Step 2. Identify the alarm system fuse
Several boxes have a diagram on the inside of the lid; if not, refer to the user manual. Recognize the alarm fuse on the diagram and then find the corresponding one inside the box. If you do not have the manual or the schematic, you will have to proceed by trial and error, following the instructions described in the next step.
- If you don't have the fuse diagram, you can find it online.
- The diagram may also appear in the user manual, if you have it.
Step 3. Remove the fuse with a pair of pliers
Once you have located the correct one, take a pair of fine-tipped pliers or specific plastic ones to extract the fuse from its housing. The alarm should go off immediately; if you cannot recognize the fuse protecting the burglar alarm using the diagram, remove and replace all the fuses one at a time until you find the one that turns off the siren.
- The alarm goes off immediately when you remove the right fuse.
- Some non-series systems may not have a fuse.
Step 4. Put the fuse back in place and see if the alarm resumes sounding
Always use pliers or plastic tweezers to reposition it when the siren has gone off. The system should have reset itself and should not reactivate once the fuse is returned to the box; if not, the plant has a problem.
- If the alarm is activated again, you must take the car to a professional auto electrician.
- If the siren resumes sounding a few minutes after inserting the fuse, there may be some incorrect setting, such as a fault with the remote control or a problem with the vehicle's ECU.
Method 3 of 3: Disconnect the Battery
Step 1. Put on the appropriate protective gear
Before carrying out any work on the vehicle, you should always put on safety equipment. Since there is a risk of sparking when working on the battery, wear safety goggles or other type of eye protection before disconnecting it. It is also advisable to use gloves to keep your hands away from the heat of the engine compartment and avoid pinching and cutting.
- Always wear eye protection when doing mechanical work, especially when inspecting electrical components.
- Gloves protect your hands from scratches, injuries and engine heat.
Step 2. Locate the battery
Typically, it is located under the hood, in the engine compartment, but some manufacturers prefer to place it in the trunk to save space or improve weight distribution. When placed in the trunk, it is usually hidden by a piece of wood covered with upholstery, which separates it from the rest of the compartment, near the spare wheel.
- If you have difficulty finding it, consult the use and maintenance manual.
- Above the battery located in the engine compartment there may be a protective cover that you need to remove in order to access the part.
Step 3. Disconnect the ground wire from the negative pole
You can recognize it by following the thick black cable that connects it to the vehicle structure or by looking for the letters "NEG" or the symbol "-" on one of the battery terminals. Using a wrench or a pair of pliers, loosen the nut securing the black cable to the negative pole. There is no need to completely disassemble the nut, just loosen it just enough to be able to pull the cable out of the terminal. The alarm, like any other electronic component of the vehicle, goes off instantly.
- Thread the ground wire along the edge of the battery to prevent it from accidentally touching the negative terminal.
- It is not necessary to disconnect the positive lead.
Step 4. Disconnect any backup alarm batteries
Some systems are equipped with a small backup battery that keeps them running even after disconnecting the main battery. It is not designed to power the siren and lights for a long time; its purpose is to keep the system active while you do maintenance work, to avoid having to reset the system when you reconnect the main battery. Consult the user manual for the alarm system or the general vehicle manual to find where the spare battery is installed and disconnect it.
- Most original anti-theft systems are not equipped with this additional power supply.
- If you don't find the backup battery, it eventually runs out by keeping the main battery disconnected for a sufficient period.
Step 5. Wait for the trip computer to reset
The time required for this varies widely depending on the vehicle model. You may be forced to leave the battery disconnected for an hour to make sure the alarm system and ECU (Electronic Control Unit) are induced to reset due to a power failure.
By forcing the on-board computer to reset, you also reset the stereo and clock settings
Step 6. Connect the battery again
After waiting for about an hour, connect the ground wire to the negative pole of the battery again. Tighten the data that fixes it and checks that it does not move; if the cable is disconnected while you are driving, the engine will shut down. The alarm could be reactivated once the cable is connected; in that case, you must take the car to a mechanical workshop for a professional repair.
- Make sure the battery cables are securely fastened and replace any covers you removed earlier to gain access.
- Start the engine to make sure there are no other problems.
