How to check the functionality of a car alarm key fob

How to check the key fob for functionality with your own hands

How to check the alarm key fob for functionality? Go to the car and press different buttons, bring the remote control to the radio and find a radio wave with a crackle in the speakers, use an oscilloscope or assemble a simple RF field detector to monitor the operation of the device. Below we will look at which methods are most effective and how to extend the life of the remote control.

Key fob diagnostics

To check and repair the device you need to do the following:

1. The key fob sends a command to open and close the doors. If the system responds to data transmission only when the user with the remote control approaches the machine, the cause of the problem must be sought in the battery.
2. If the alarm key fob does not work, the battery is removed from the communicator.
3. The key fob is being disassembled. To disconnect the body parts, use a Phillips screwdriver to unscrew the bolt that secures them to each other. The fixation element can be located either on the cover or in the compartment under the battery. After disassembling the case, the keys are removed.
4. If the cause of the problem is a failed display, the screen is immediately replaced. It may have cracked, causing shards to fall onto the board or making it difficult for the keys to move. The electrical circuit needs to be cleaned.
5. A visual check of the board is performed. If traces of oxidation or exposure to moisture are visible, the device must be dried.
6. The graphite cable is disconnected from the communicator board. Using a dry brush, the contact tracks are cleaned.
7. The integrity of the buttons is checked. If the controls do not click or are stuck, they will need to be replaced. To fix the keys, you should build up wire needles, which will be used to transmit a signal when pressed. The buttons are attached using a soldering iron.
8. The screen is installed in place; it must be fixed with glue. You need to act carefully so as not to fill the display with liquid.
9. The board is installed in place, the case is assembled. At the final stage, you need to insert the battery into the rear compartment and check the quality of operation.

Video: repairing a key fob at home

The “Eugene Irimia” channel, using the example of a DaVinci alarm communicator, showed the process of restoring devices.

How to check if the key fob is working

During the operation of the alarm system, car owners often encounter situations related to malfunctions of the device. In such circumstances, you need to know how to check the alarm key fob in order to decide what to do next - try to repair the device or order a new device on the Internet.

Preliminary steps

Before testing for functionality, take the following steps:

Control methods

Now let's highlight the basic methods of how to check the alarm key fob for functionality. To do this, use one of the following options:

If you cannot check the alarm remote control on your own, you can contact a service center. The technicians have the necessary set of equipment that allows them to diagnose the device and determine whether it is functioning or not. Here a decision is made about the possibility of repair.

Where and how to buy

You should not order a keychain on cheap Chinese sites. Firstly, there is a high probability that during its transportation the somehow assembled microcircuit will be damaged and the device will become inoperative. Secondly, there are no guarantees that the key fob will last at least a month and will correctly reflect information (not to mention responding at a distance).

If you want to get a high-quality keychain, our online store will offer competitive prices for devices and qualified assistance in choosing.

Recommendations for using the key fob

When using a two-way remote control, many people forget that it is a fragile device that tends to break. To extend the life of your device, you need to follow several tips:

Knowing how to check the alarm key fob for functionality, you will be able to diagnose a breakdown in time. If you follow the operating rules, you can extend the life of the product. In the comments, share your experience of checking the remote control and methods of protecting it from malfunctions.

Source

Remote control diagram

The alarm key fob is a complex radio-electronic device. It is not appropriate to examine the scheme in detail within the framework of this article. If you need to repair it, contact a professional.

The elementary circuit looks like this: the heart of the device is the control chip. It receives signals from the buttons on the key fob, processes them and, through an antenna installed in the body, transmits a specific code at a certain frequency to the control unit of the car. Also, through the antenna, the microcircuit receives a signal from the unit, analyzes and displays information on the screen, or signals with an audio signal. The sound is produced by a miniature buzzer.

How to check the alarm key fob for functionality

In this article, car mechanic Alexey Bakulin answers a popular question from readers, “How to check the alarm key fob for functionality?”

Car owners are often faced with a situation where the alarm does not respond to the key fob. As a result, you have to open the car with the key, which leads to the siren going off and not the most pleasant experience. What to do when the alarm does not respond to the key fob and how can you eliminate the reasons leading to the failure?

The reasons why the alarm does not respond to the key fob can be very different. Most of them can be easily fixed without contacting car services or specialists who install security systems. Repairing car alarm key fobs is a simple procedure that any car enthusiast can perform.

If the car does not respond to the alarm key fob, then there is a high probability that the batteries in the key fob are low or have moved out of place. A gradual decrease in battery charge is often accompanied by dimming of the LED and screen.

The situation can be corrected by simply replacing the battery. To do this, the body of the key fob is opened, which is then gently tapped on a hard surface. The battery should fall out of the socket. After a new battery is inserted into the alarm key fob, the system will begin to respond to key presses.

Often, such zones are located in close proximity to closed facilities, airports and sensitive enterprises. The source of interference can be an electromagnetic field, a large concentration of transport or cash-in-transit vehicles, which is why you should not stop next to them.

You can check whether this is the reason why the alarm does not respond to the key fob by holding the device close to the receiver and pressing the corresponding key. If such measures are useless, then the car must be driven several hundred meters and the procedure repeated with the key fob.

The operating voltage of a discharged battery is not enough to turn on the alarm system. In addition, the alarm beeps and does not respond to the key fob if there is severe frost outside.

Many transmitters do not operate if they are outside the signal range and the buttons are pressed repeatedly. This often happens when the keychain is in a trouser pocket or small children are playing with it.

The response radius of alarms that have been in operation for a long period of time may decrease over time. One of the reasons for this may be the failure of the transmitter signal reception antenna, which is mounted in the car. There is a possibility that errors were made during installation of the system that led to such consequences.

In such cases, the transmitter cannot communicate with the system, and accordingly, the alarm does not respond to the key fob. What to do in such a situation? Go to a specialist who can reflash the alarm unit. To do this, you will have to turn off the entire system in an emergency way. Repairing car alarm key fobs by reprogramming can be done on your own - as a rule, the entire process is described in the operating manual for the system and is a simple algorithm performed by pressing a certain sequence of keys.

Not every car owner can independently repair a car alarm or its remote control. For those who are unsure of their abilities, there are several methods for bringing a broken system back to life.

Emergency shutdown option. Any car security system can be forcibly disabled using a special code. It comes complete with the alarm and is installed during its installation. In order to enter a digital combination, you need to use the Valet button - it is located next to the steering wheel of the car, on the center console or not far from the unit. The code can be either a sequential chain of key presses on the key fob or any other combination.

The place where you purchase the battery is important. It is not worth buying batteries outside in severe frosts - after they warm up, their service life will be reduced significantly, and there is a high probability that they will discharge immediately after installation. In addition, you should have a spare set of batteries with you in case the remote control stops working.

Preparation for the procedure

For those who are wondering how to reprogram a key fob, it is important to remember that preparation for such a procedure is necessary. To do this you need to follow these steps:

• If you lose your key fob, you need to purchase a new device only of the model that was included with the installed alarm system.
• If several radio transmitters are used to control the system, they must be reprogrammed at the same time so that they can be assigned to the new control unit.

Many suppliers include instructions in the kit. In this case, the user may have difficulties when there are no tabs with a translation of the instructions into Russian or they are written with errors (if the device was manufactured in Korea).

The motorist must first read the attached instructions. This document should show the design of the remote control. If there is no manual, the user should follow the generally accepted instructions.

Why does the car key fob not work?

Are you, dear friend, faced with the problem of disabling your car from the security alarm system, or is your car no longer responding to the alarm key fob? Or maybe your car, equipped with a keyless entry system, has stopped recognizing your key fob and does not remove the car from security? Well, what do we want to tell you, friends. Surely many motorists face these or similar problems every day. Today, our online publication 1GAI.RU invites you, gentlemen, to familiarize yourself with a detailed description of these various and various problems related directly to remote key fobs. You can also find out for yourself why car remote key fobs most often stop working and what needs to be done in such problematic incidents.

There are several main reasons why a car's remote key fob may stop working. To your and our happiness, each driver will be able to independently determine the cause of the alarm key fob malfunction.

The most common problem with any car key fobs is the discharge of their internal battery or wear out of the power supply battery. Therefore, such a battery replacement should certainly solve this emerging problem.

But sometimes such a replacement of the battery in the key fob, unfortunately, does not help. As a result, an incident may occur; replacing the old battery with a new key fob may simply not be detected by the car alarm itself. This problem most often occurs in cars that are equipped with a keyless entry system and push-button engine start.

If your car, after replacing the battery in the remote key fob, does not respond to pressing buttons and does not open the doors, even if the driver came almost close to his vehicle with the key, then you may need to reprogram the key fob itself.

In most cases, you can do this yourself without using various electronic equipment. In some brands of cars, even after replacing the battery in the alarm key, you may need to contact an official dealership with this problem to reflash the electronics unit.

Is it possible to replace the old key fob with a new one?

The short answer is yes, you can change the remote control, but it’s not easy.

Previously, alarm systems were based on a permanent, static code that was easily picked up by attackers. Modern systems use dynamic code, and they work on a dialog principle, which looks like this:

• after pressing the button from the key fob, the ID number is sent to the base alarm unit;
• this number is checked by a system that “knows” the pattern on the basis of which it was generated;
• if the check is successful, the base unit generates its own response number, which it sends to the key fob, after which the car owner gets access to the main alarm unit and can turn it off.

From all of the above, it becomes clear that after purchasing a new key fob, you will have to “register” it in the existing alarm system, i.e., make sure that the system begins to consider the new device “its own.” How to do this depends on the alarm model. In most cases, when replacing a key fob, it is necessary to completely reflash the software in the base unit, and this can only be done by a qualified specialist.

It’s not difficult to purchase a new key fob, but only a specialist can “link” it to an existing car alarm.

The car does not respond to the remote control alarm

If you encounter, for example, a case where when you press the alarm unlock button your car does not respond at all, then you must first find out for yourself whether the cause of the malfunction really lies in the key fob. After all, it is quite possible that your alarm key fob is in good working order and the problem lies in a breakdown of the car’s electronics or in the failure of the anti-theft security system itself.

To find out if your car's remote key fob works, you need to take a second spare key fob and use it to try to open and lock your vehicle . It's worth noting here that most vehicles come from the factory with two key fobs or remote keys (some car companies even ship vehicles with three smart keys).

Thus, in order to establish the reason for the key fob failure, you need to check whether the second spare remote key works. If the car still does not respond to the second (spare) key fob, then most likely the problem is not related to the remote key itself.

In this case, the problem will most likely be related to the electronics of the car itself . For example, most often it may be a mechanical or electronic malfunction of the door locks of a given vehicle. Also, it often happens that the car simply does not see the key due to a breakdown of the car alarm receiving antenna.

If your backup or emergency (spare) remote key fob opens the car and closes it without any problems, this means that the main key fob for the car is inoperative and this problem is not related to a malfunction of the car door locks. In this case, and most likely, the power element (battery) in the key fob has run out.

Unfortunately, not all car owners have a second spare key fob for their car. In this case, you need to check the functionality of the battery of the key itself.

Firmware methods depending on the alarm model

After the service button has been found, the process of recording key fobs into the alarm memory should begin. Depending on the models, one firmware method should be used.

Method 1

• Disarm, turn the ignition switch to the (Lock) position.
• Press the (VALET) button repeatedly (7 times), each time the button is pressed the LED should blink.
• Turn on the ignition, the alarm will notify you of entering the service mode with 7 beeps.
• As soon as you enter the service mode, press and hold buttons 1 and 2 on the key fob simultaneously (for B6D, B9D, B61, B91, A61, A91, buttons 2 and 3), the key will be registered in the alarm unit.
• When the key fob is successfully recorded, 1 beep will sound. If you need to bind a new key fob, then immediately after programming the first one, take the second key fob and press buttons 1 and 2 again. As soon as the key fob is registered, the alarm will notify you with a sound signal. If it was not possible to reprogram the key fob, the alarm unit will exit and switch from the service mode to the standard mode (the turn signals flash 5 times).
• When all the key fobs are stitched, you need to turn off the ignition, the alarm will exit the programming mode (the turn signals flash 5 times).

Method 2

• Disarm, turn the ignition on, then press and hold the service button for 6 seconds, after which 4 beeps will sound (service mode is on).
• Immediately after entering the service mode, press and hold buttons 1 and 2 on the key fob simultaneously, the key will begin to register in the alarm unit.
• If the key fob is registered correctly, 1 beep will sound. If you need to record an additional key fob, then immediately after recording the first one, start recording the second key fob, to do this, press and hold buttons 3 and 4. After recording the next key fob, the alarm will notify you with a signal, the number of signals depends on the order of the key fob for recording.
• If the key fob has not been recorded, the alarm will exit the service mode (the turn signals flash 5 times).
• After recording the required number of key fobs, turn off the ignition, thereby disabling the alarm from the recording mode (the turn signals blink 5 times).

Check the battery in your car's remote key fob

Most remote car keys or alarm fobs use 7 types of batteries. In some cars, instead of batteries in the keys themselves, rechargeable batteries are used and are recharged from the ignition switch while the car is moving. True, in recent years, automakers have mainly begun to supply new cars with key fobs that are powered by batteries.

Thus, it turns out that most often drivers of all modern cars that were produced by the plant quite recently encounter discharge of batteries in car key fobs. Including, many car owners, in addition to the standard car alarm system, equip them with additional security systems to reduce the likelihood of their theft.

As a rule, most of these non-factory car alarms also come with remote controls with which the driver can open and close the car. Such remote controls are usually also equipped with regular batteries.

As a result, sooner or later, like any battery, they (remotes) will completely lose their charge and the car key fob or the same key fob for an additional alarm will simply stop working. In this case, you will have to (have to) replace the old battery with a new one.

Also, the next way, you can find information about the key battery in the car’s operating manual or on a forum on the Internet, or call the dealership directly. Naturally, it will be much easier to do everything yourself, that is, just open the key fob and look at the battery markings, which, as a rule, are applied to the surface of the battery itself.

For example, many vehicle owners equip their cars with non-standard security systems in addition to the factory ones. As a rule, these additional car alarms come with remote key fobs (remotes) with which you can remotely turn on/off the security system of such a vehicle.

In most cases, these similar remote controls use the following batteries as batteries: A23 (12 Volts), A27 (12 Volts) and AAA “pinky” (1.5 Volts).

Once you know the type of battery, you can safely check its voltage using the same multimeter.

Also, if you have a new battery, then you can simply take and install it to replace the old one, and then check the functionality of the key fob. If, after replacing the battery, your car begins to respond to the key, then the cause of the malfunction was hidden in a discharged battery.

But, if after installing a new battery, the key fob still does not work , and the second spare key opens and closes the car without problems, then most likely the contacts of the battery compartment in the key fob are damaged or there is a malfunction of the key buttons themselves.

In particular, it is necessary to remember that in some car models, after replacing the battery in the alarm key fob, reprogramming of the electronic alarm system is required, which, after a long discharge of this key fob, simply forgot it.

Spontaneous operation

Spontaneous activation of the “alarm” may be due to the following reasons:

• problems with door mechanisms;
• incorrect operation of sensors;
• environmental influence.

Problems with door mechanisms

If the door mechanisms malfunction, the cause should be sought in the following elements:

• fuses - devices could have burned out or parts that did not meet the rating were installed;
• wires for connecting door locks - electrical circuits wear out and are interrupted;
• limit switches (triggers);
• central locking - mechanical damage to one of the structural components or breakdown of the control unit.

To check the operation of the lock products, insert the key into the driver's door and lock the car. If the central locking is working, then all devices should be locked. Otherwise, it is necessary to check all connectors for products installed in each door, as well as the integrity of the electrical circuits. In fact, the cause of the malfunction is usually a lack of contact on the central locking control unit block.

The cause of the problem may also be a disconnected contact from the trigger. To resolve the problem, reconnect the cable.

It is important to know

If the triggers break down, the devices are replaced immediately. These parts are inexpensive, so there is no point in repairing and restoring them.

Incorrect operation of sensors

If the sensors are not configured correctly, the alarm will turn on the alarm mode for no reason, reacting to passing cars and running animals. Moreover, the system can be activated in strong winds.

To eliminate the cause, you must perform the following steps:

1. Disconnect all electrical equipment in the vehicle and turn off the ignition system.
2. Gain access to the controller that is to be configured. The main requirement for such devices during installation is their placement in the central part of the body. Because of this, their installation is usually carried out on a panel separating the engine compartment from the car interior.
3. After gaining access, the cable and the quality of the sensor connection are checked. If necessary, replace the electrical circuit and clean the contacts on the connector from dust and oxidation.
4. The sensitivity of the sensor is being changed; the operating parameter should be set to a minimum. For this purpose, devices are equipped with special regulators that need to be turned counterclockwise. Some systems are equipped with three- and two-level sensors that allow you to change the sensitivity of the alarm or warning zone.
5. When changing the operating parameter, it is recommended to check the operation of the controller by periodically tapping the vehicle body.

Video: adjusting the car alarm shock sensor

The “AVTOservis Nikitin” channel in its video showed in detail the process of changing the sensitivity parameter of the shock controller.

Environmental influence

Incorrect operation of the alarm may be due to two factors related to environmental influences:

1. High humidity outside will lead to dampness of the contacts and components of the system. To fix the problem, you need to either dry out all structural components or wait until the weather stabilizes.
2. Low temperatures. Severe frost will cause the system to take longer to respond. The alarm carries out commands sent from the key fob, but does so with a delay. It is possible that the alarm will not respond to remote control presses at all. The only thing that can be recommended here is to park the car in an insulated garage.

Faulty battery contacts in a car key

Unfortunately, not all drivers handle car keys, electronic key fobs and security system remote controls with care. For example, it most often happens that car enthusiasts simply drop these keys, and sometimes even fill them with water. In this case, as you know, any key fob can be damaged.

The most common failure of a key fob is damage to the battery contacts, as well as wear and tear on the buttons themselves.

The best way to check the key contacts or the wear of the buttons on the key fob is to visually inspect it. To do this, you need to remove the battery from the remote control and carefully inspect the contacts themselves. If the contacts have oxidation or other damage, then the reason for the key failure lies precisely in this. It is also necessary to check whether the battery terminals are tightly installed. If the contacts move freely, then there is damage inside the key at the junction of the battery contacts with the remote control board.

Setting up the Sherkhan alarm

Before working with the Sherkhan alarm system, you need to disarm the system. Next you need to complete the following steps:

• First, you need to press the Vallet button so that the alarm lights flash.
• Next, you should click Vallet again. As a result, the LED will start blinking.
• After this, you need to press Vallet as many times as there are numbers in the PIN code. This step must be repeated for all digits of the PIN code.
• 6 seconds after the last digit of the code has been entered, the alarm will flash. Thus, the system will confirm its readiness to enter the code.
• Within 4 seconds, you need to briefly press the fourth button on the first key fob 2 times. If the recording is successful, the alarm will automatically flash.
• After this, you can enter the codes of the remaining key fobs. If the code is entered successfully, the alarm will flash.

To exit reprogramming mode, you do not need to take any action for 5 seconds after the last code was written. As a result, the alarm will flash and the system will exit reprogramming mode.

Reprogramming a car's remote key after replacing the battery

In order for the remote control for keyless entry into the car to work properly, it is necessary that it be reliably connected via a radio channel to the radio receiver unit of the car's security system. Thus, if the battery in your remote control runs out, the car will no longer be able to recognize you as the owner of the car and will not disarm it.

Unfortunately, many car models sometimes simply stop detecting keyless entry key fobs after replacing their batteries. This is due to the fact that the key fob itself and the car’s security system cease to understand each other over the radio channel. In this case, it is necessary to reprogram the keyless entry system for the vehicle. Also, some car models supplied with conventional remote keys may also stop recognizing key fobs after changing the battery in them.

To restore the functionality of the remote key fob, some car models can be opened with a regular mechanical key, and then inserted into the ignition switch itself (if you have a stop-start button instead of a key, then it must be removed to gain access to the emergency ignition switch connector) and initialize the remote control in which you previously changed the battery, and all this must be done according to the vehicle’s operating manual.

To our regret, we cannot, within the framework of today’s article, describe all the available methods for restoring the functionality of a key due to its desynchronization after replacing the battery, since each automaker has previously provided its own individual method for reprogramming key fobs and keyless entry remotes to the car.

We will describe for you only the most common methods of such reprogramming, which will help you register a new key, a new remote control, a new key fob or a new remote tag for the keyless entry system into the car in the electronic unit.

Next, you need to turn the key to the working position, but without starting the engine. Then you need to turn the key back to its original position. And so you need to repeat everything several times until you hear a sound signal from the car, which will tell you that the security system has entered programming mode.

Then, after the sound signal, you need to press the button to unlock or lock the car on the remote control itself, after which a sound signal will also be heard, which will inform you that the new key has synchronized with the car alarm.

In some car models, in order to enter the key programming mode, you first need to insert the key itself into the ignition switch and then pull it out again, and this must be done at least 6 times within 10 seconds. If your car uses this particular method of synchronizing (programming new key fobs) remote keys, then if the actions are correct, you will see clearly how the external light lights begin to blink (in some car models, certain icons or symbols may begin to blink on the instrument panel hazard warning lights).

After the lights flash, you must insert the key into the ignition and turn it until the instrument panel turns on. Please note that you do not need to start the engine itself. Otherwise, your car will automatically exit key programming mode and you will have to start all over again.

After you have turned the key to the position that turns on the dashboard, you need to press the car lock or unlock button on the key fob. If you did everything correctly, you should see the external lights flashing or the hazard warning lights (hazard lights) flashing.

Unfortunately, but this is a fact, not in all car models it is so easy to synchronize a new key yourself or re-register the key fob after replacing its battery. In some vehicles this may require special equipment. In this case, you will have to contact an official dealership or an unofficial auto repair shop that has experience working with your make and model of car.

If your car is equipped with an additional non-factory security system, including one that also comes with a remote key fob, then you need to refer to the written manual for this alarm system in order to find out how the special key reprogramming mode works in the security system.

Core Technology

The key fob reprogramming technology is simple. To do this you need to do the following:

• By installing the key in the lock, the user must activate the ignition. There is no need to start the power unit.
• Next, you need to simultaneously press with one hand the button with the loudspeaker and the button with the image of the luggage compartment. With your second hand, press the “service mode” button.
• When the speaker beeps 5 times, you can release the pressed button.

Having correctly completed the proposed actions, the motorist must again press the button with the image of a loudspeaker and the button that opens the luggage compartment. As a result, the turn lights should flash several times.

It often happens that as a result of these actions the key fob is still not programmed. In this case, you can repeat the reprogramming along with recording the key fob. Another way is to reprogram the key fob without a code . To do this you need to do the following:

• Within a few seconds, you need to connect and turn off the ignition system 3 times by turning the key.
• If the motorist has done everything correctly, he will see a single flash.
• After the flash is fired, the owner will have 4 seconds to press the communicator registered in the memory.
• After recording on the first electronic remote control, the user can press a key on another key fob.
• Information from the third key fob must be entered into memory in the same way. When recording the last remote control, information from the first device will be deleted automatically.

After the last remote control has been reprogrammed, you need to wait a few seconds. This is necessary to exit the recording.

Damage to the car security system

If all the methods described above did not help you and your car still does not see a working remote key, then most likely the problem is hidden in the security system itself. Perhaps the alarm antenna itself is damaged in your car or the electronic receiving radio unit has failed. In this case, you need to contact electronic alarm specialists or an official technical dealership.

It is also necessary to remember that if your car does not see the remote key fob even after replacing its battery, then it is quite possible that the car key is faulty and requires repair. In this case, repairing it can be very expensive. So remember, friends, it’s better to order a new key from the dealer and not suffer.

It is also worth noting here that key fobs for used cars are widely available on the market these days. Compared to new keys, these used key fobs are very cheap. But you must remember that in this case it is unlikely that you will be able to independently register the key in the security system of your vehicle.

So the possible and imaginary savings of buying a used someone else’s key fob may ultimately result in unnecessary costs for you. Trust us, friends, it will be easier and more profitable to buy a new key fob. Success and good luck friends!

Source

The need for reprogramming

There are various reasons when key fob programming is required. For example, when a user bought a new car with an already installed alarm system. In this case , it is better to reprogram the key fob so that unauthorized persons cannot disable the security.

Of course, you can do without flashing it, but if you buy an expensive car, such a procedure will not be superfluous. This procedure is also a solution if the owner loses the alarm key fob. The question of how to program a key fob also becomes relevant in the event of software failures. For example, when the device issues commands incorrectly.

In this video you will learn how to reflash the key fob:

The price for such a service depends on the complexity of the system. The average cost of reprogramming is 500 rubles. However, such work is simple, and, following the instructions, the user can do it himself.

This is interesting: How to set up a Starline alarm key fob

The most common malfunctions in car alarms

All alarm malfunctions can be roughly divided into the following types:

• eating problems;
• wiring problems;
• software failure;
• false positives;
• There is a problem with the key fob.

Let's take a closer look at each of the car alarm malfunctions.

Eating problems

Troubleshooting car electrical problems, installing car alarms and immobilizers. As well as comprehensive diagnostics and repair of cars of any foreign cars, the Otkritie car service provides.

Wiring problems

Software failure

False positives

Faults in the key fob

How to find a fault in a car alarm

You need to start with the keychain. Inspect it for mechanical damage and traces of water. If the key fob gets into water, condensation will form on the inside of the display cover. The operation of such a device (if it turns on) will be unstable. If the key fob does not fall and falls into the water, but the display is turned off and nothing happens when you press the buttons, then the culprit is a low battery.

If the key fob is fully operational, but nothing happens when you press its buttons, then there may be two reasons for this - strong external interference or problems with the car and the alarm system.

Try bringing the key fob to the part of the car where the car alarm antenna is installed and press the button.

If nothing happens, then faults must be looked for in the machine itself or in the alarm equipment installed on it.

Next, power and wiring diagnostics are performed. Check the battery charge and inspect its terminals for oxidation. The full charge of the battery can be easily determined by the operation of the on-board electronics. If everything is normal, then the next step is to check the wiring.

To do this, you will need a special tester that calls contacts. Inspect the wires for mechanical damage. Special attention should be paid to fuses.

They are usually found in a box, which is located on the wire coming from the positive terminal of the battery.

If the cause has not yet been found, then a defect in the control unit or a malfunction of its software is to blame. You won’t be able to eliminate such a defect with your own hands, but with a software failure everything is much simpler - you just need to carry out simple manipulations, which we will discuss below.

Do-it-yourself car alarm and key fob repair

Most often, when a key fob falls, quartz breaks off from its board. To eliminate this defect, it is enough to disassemble the key fob and solder the quartz in its original place.

To fix cracks in the display, you need to completely replace it. Remove the old display, clean the contacts and solder the cables of the new display.

The process itself is not very complicated and requires basic soldering skills. The difficulty lies in finding a new display. You are unlikely to find it in stores, so you will have to order from China via the Internet.

Defects caused by water ingress cannot be eliminated on your own.

Power and wiring problems can be resolved by stripping the battery contacts and terminals, as well as replacing fuses and damaged wires. To avoid unnecessary work, use the tester to find the exact cause of the problem and then fix it.

To resolve software glitches, you must reboot the system. To do this, turn off the power by disconnecting one of the terminals from the battery for a few minutes. If this does not help, then reset the car alarm to factory settings. Step-by-step instructions for resetting settings can be found in the instructions for your alarm model.

How to check the operation of a car alarm

Most problems associated with the operation of car alarms can be eliminated with your own hands. Repair of the control unit and other complex electronics is best left to specialists. If after following the above recommendations the breakdown is not resolved, then you need to contact a car service. To continue driving with a broken alarm, you need to master the process of turning it off with a secret button, which you can read about in the instructions for the car alarm.

Common faults

The need to disassemble and restore the operation of the device occurs when the following problems occur:

1. Failure of the battery or oxidation of the contacts inside the compartment. A low battery will cause the anti-theft system to stop responding to commands transmitted from the pager or to do so unstably. In this case, the display of symbols under the glass will be dimmer, and the blinking color of the LED light will also deteriorate. To restore the device yourself, you need to change the battery, and you will have to disassemble the pager if you need to clean the contacts.
2. Damage to the display. This malfunction is usually caused by a serious physical impact on the pager body. In case of critical hits, a protective cover will not be able to save the situation. If the screen fails, the user may still be able to control the security mode and some other options. However, additional functionality will not be available to the consumer, since configuration requires the use of the display in any case.
3. One or more buttons on the communicator have fallen off. Over long periods of use, the controls will wear out, which can cause them to stick. If the button fails, to restore the functionality of the key fob, the user will have to disassemble the remote control themselves and carefully check the board. Before replacing the key, you need to purchase a new part. In practice, the cause of the problem is usually a damaged contact on the control element, so re-soldering the button is usually enough to fix it.
4. Damage to the pager body. Frequent falls can cause scratches on your device; over time, more serious defects may develop. Keyrings from Starline are generally characterized by low strength, so it is better to prevent them from being hit. The device must be repaired if there is serious damage, since liquid can get onto the board through a crack in the case.
5. Hardware faults are usually caused by moisture in the pager circuitry. During prolonged operation in conditions of high humidity, capacitors, as well as other elements of the remote control, fail. Do-it-yourself repair in this case consists of disassembling the device body and drying it. You cannot dry your communicator on a household stove or with a hairdryer, since high temperatures can completely damage it. To dry, it is recommended to place the device in a warm place, for example, on a radiator, for several hours.

Video: troubleshooting the key fob

In a video, user Alexander Shkurevskikh showed the process of identifying problems in the operation of a car pager in the absence of feedback.

Video: DIY repair of the Starline key fob

The AlanMorfreeman channel in its video showed in detail the process of resoldering the contact elements on the communicator to control the Starline alarm system.

Recently, the fleet of car alarms has been changing to new, more advanced and burglary-resistant ones, with interactive code and expanded functionality. The old ones remain out of use, but they can be used for other needs. Let's look at the circuitry of their radio path, which operates at a frequency of 433.920 MHz, allocated for this in Russia.

The earliest simple models used a super-regenerative receiver circuit. Despite their simplicity, they have disadvantages: low sensitivity, low selectivity, spurious radiation of a radio signal into the antenna (without appropriate circuit solutions), etc. A typical diagram of such a receiver:

A typical circuit of a simple transmitter for it:

The ability of a super-regenerative receiver to simultaneously emit and receive a signal in a similar circuit, but without a preliminary amplification stage, and switched to the autodyne operating mode, is used for benefit in microwave sensors for various security alarms, which are a further evolution of the radar fuses of shells and bombs of the Second World War : Scheme from the patent (not according to GOST):

Brief job description (secret):

Is it worth continuing (there is no military blog)? And they, in turn, probably got the idea from the theremin. A good description of the operation of such a receiver can be found here: nenuda.ru/super-regenerative-receivers.html You can find a lot about the microwave volume sensor in the literature and on the Internet. radiokot.ru/circuit/analog/receiv_transmit/27/ As well as about the radar fuse, if someone is unlucky in life, he studies and serves in the relevant institutions: ru.wikipedia.org/wiki/Radio fuse

Then they switched to more advanced superheterodyne receivers, both with single and double frequency conversion. The appearance of radio components in miniature surface-mounted packages, whose dimensions are disproportionately smaller than the wavelength at the operating frequency, makes it possible not to bother with this method of mounting high-frequency circuits, which has thrilled more than one generation of radio amateurs:

As a rule, the radio circuit diagram in the alarm key fob and in the alarm module itself is not noticeably different. Both amplitude modulation and frequency modulation are used.

For example, this is what a transceiver board with amplitude modulation and one frequency conversion looks like:

And so with frequency and double frequency conversion:

This is what the key fob board looks like, which only has a transmitter:

The other side is in the title.

The diagram of the radio frequency part of the transceiver is approximately the same as in the picture:

The components of the transmitter and receiver up to the mixer, signaling with amplitude modulation, or as is customary with “them” - manipulation (ASK - amplitude shift keying) are painted in the upper part, and on the lower part - with frequency modulation (FSK - frequency shift keying). Next, in the node responsible for receiving, there is, as a rule, a specialized microcircuit, in a typical circuit for its inclusion. There are many options, I’ll give you a couple: Continuation of the receiver circuit from the top:

Continuation of the receiver circuit from the bottom:

A little about the purpose of some components: SAW resonators are used as the frequency-setting circuit of the transmitter and the receiver local oscillator. SAW (SAW) resonators use the effect of surface acoustic waves and, unlike quartz resonators that use the piezoelectric effect, have a higher operating frequency (frequency range from 100 MHz to 1.1 GHz), but less stability (from 20 to 200 kHz (30-250 ppm)). SAW resonators are available in surface-mount and through-hole packages. And since SAW resonators and filters have a greater spread of characteristics in terms of resonance frequency, bandwidth, etc., than quartz ones, it is often necessary to adjust the frequency of the transmitter oscillator and receiver local oscillator using a variable capacitor. The marking of ceramic resonators on the board is not always informative; on the body of the transmitter and local oscillator resonator, one frequency may be indicated, and the frequency of the local oscillator resonator differs from the frequency of the transmitter resonator by an intermediate frequency (10.7 MHz, 21.400 MHz, etc.). Their difference can be indicated by a letter or number, for example, T-transmitter, R-receiver. The antenna, depending on the operating mode of the transceiver, using pin diodes (circled in red), switches either to the output of the transmitter or to the input of the receiver. Let me remind you that Pin is a diode, it has the ability to pass a high-frequency signal through itself (or shunt), in the presence of a small direct current through itself. And the diode circled in green at the bottom left is a varicap. Its capacitance varies depending on the reverse voltage applied to it. This allows, within certain limits, to adjust the frequency of the transmitter generator built on a SAW resonator. This diode is supplied with modulation voltage from the microcontroller. After detection, the signal from the receiver chip is fed to the microcontroller for decoding. Diagram of a key fob, without “feedback”, equipped only with a transmitter:

How to repair car alarms: replacing quartz and other methods

It would seem that it would be easier to just take and replace the battery in the alarm key fob. The owner himself can perform this action without errors. Only now, after the replacement, the connection between the key fobs and the signaling is lost for some reason.

In reality, a loss of synchronization occurs, and the consequences of this “loss” can be corrected according to the text of the manual supplied by the manufacturer.

Here we consider what actions should not be allowed when repairing car alarms, as well as immobilizers and key fobs.

Key fob repair tips

A feedback key fob, or so-called pager, contains several elements in its design. The display is connected to the printed circuit board via a cable. But soldering this part (loop cable) is difficult in practice. This is precisely why the replacement operation has an increased cost.

Signaling pager circuit board

However, you can perform this replacement yourself. Which is proven in the video.

After disassembling and opening the plastic case, you will notice an important part covered with a metal shell. The cylinder is a watch quartz, and you need something similar.

Radio module printed circuit board

Let's say the pager display shows that there is no connection. In this case, repair of the alarm key fob is carried out as follows:

1. Solder the connection point with the antenna, perform assembly and testing;
2. If the defect remains, replace the main quartz.

In general, repairing car alarm key fobs does not involve searching for defects using special equipment. They are more often guided by logic, changing “suspicious” components and parts. They also strive to eliminate mechanical defects: they replace button modules and restore contacts. The main thing is to remove all power elements before soldering. And wait 20 seconds.

Any button can be replaced

Repairing a key fob with your own hands is a painstaking and difficult job. Having removed any battery, it will be necessary to restore synchronization. But equipment working with dialog code does not lose synchronization.

We repair the standard immobilizer ourselves

Any modern car has a module installed that automatically blocks the engine. Such modules are called “immobilizers”, and their malfunctions are characterized as follows:

• You cannot start the starter even with your own (standard) keys;
• Commands from the remote control (key) buttons are not perceived in any way.

Sometimes the problem lies in the electronics of the remote control. But hardly anyone will undertake to repair it.

Remote key for LADA cars

Here we discuss how to repair the immobilizer, more precisely, the antenna and the main unit. The block itself, at least, can be disassembled by hand without using special equipment.

Case Study (GF-626)

The standard equipment of the MAZDA GF-626 is an immobilizer, in which the main communication frequency is set by a ceramic resonator. The specified part looks like this.

Standard unit MAZDA GF-626

Over time, the parameters of parts change. Therefore, repairing the immobilizer will consist of the following: unsolder the “bad” resonator, install a new quartz in its place. The frequency of the quartz resonator can be selected experimentally (here the numbers 2.4576 are indicated on the case).

Main unit after repair

Let us make a digression regarding the choice of resonators. If you buy a replacement quartz with the corresponding numbers, you may not always get a good result. The reason is the following:

• Low thermal stability;
• Frequency jitter.

In general, a new part is selected as one of several. What you need to know when repairing an immobilizer, key fob, and even an alarm system. Who said it would be easy?

Inductive antenna repair

The immobilizer reads data from the key, establishing radio communication with it. The following is typical for standard automotive systems: an inductive antenna is wound around the ignition switch. Let’s say you can’t start the starter even with your own keys, which are programmed into the memory of the main unit. Then the immobilizer repair begins with checking the antenna, completely disconnecting it from the connector.

Antenna removed from the ignition switch

The appearance of the antenna module is shown in the figure above. It may turn out that the resistance between the black and white wires is infinity (open).

The connector was connected to the immobilizer

No one can wind such a reel by hand. But you can do the following:

• A soldering iron without solder is placed between the turns, and each turn is passed until the ohmmeter shows 5-10 Ohms;
• The gap is eliminated, even with the appearance of short-circuited turns.