Modern car security systems reliably protect against theft, but they themselves can become a source of problems. The most common of them is alarm does not respond to key fob, preventing you from disarming the car or turning it on.
Accustomed to doing without a key, the car owner sometimes cannot even get into the car without outside help. Most often, the culprit of such troubles is the key fob itself, but failure of the main unit of the security system or external factors cannot be ruled out.
You can find out how to find the cause of the problem and what to do when the car does not respond to the alarm key fob and does not allow you to unlock the doors from our article.
Why does the car not respond to the alarm key fob?
The reason for the lack of response of the alarm system to pressing the key fob buttons can be either the failure of the components of the security system itself - the key fob, transmitter, main unit, or external barriers that prevent the transmission and reception of the signal. You can understand why you can’t disarm your car or turn on the alarm with the key fob by looking at a combination of characteristic signs. The table below will help with this.
| Signs | Most likely causes |
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There may be no connection between the key fob and the central alarm unit if the car battery is completely discharged. How to open a car if the battery is dead is written in a separate article.
In addition to the actual malfunctions and interference, the reason that the alarm does not respond to the key fob may be an unsuitable case. Most often, this problem occurs when using non-standard silicone products without slots for buttons. The owner may have the feeling that the key fob reacts to pressing the buttons every once in a while. In fact, they simply do not sink in completely and do not make contact.
Let's sum it up
Alarm problems are one of the most difficult types of vehicle breakdowns. Therefore, when problems arise with the security module, car owners prefer to go to a service station and perform all the necessary tasks quickly and efficiently. But you can refuse to pay quite large bills and specialist services. To do this, you just need to find all the working elements of the alarm system, acquire a tester or other electronic device for measuring electrical connections. This will help you complete the necessary tasks quite simply.
The car owner can easily find and even fix most alarm problems on his own. It is enough to follow the instructions, and also read the relevant sections of the instructions for the security system before disassembling. Reading the instructions may fix all the problems on its own, since in this case you can fix most problems quite simply by pressing a few combinations of buttons on the remote control. If your car starts having problems with the alarm system, you should perform a quality restoration, if not on your own, then with the help of specialists. Have you ever had problems with the security system while operating a car?
Basic malfunctions of the car alarm key fob
5 possible causes of key fob failure: video
If the alarm does not respond to the key fob due to external interference, only changing the parking location or replacing the security system with a more noise-resistant one, controlled via GSM or via a mobile application, will help. To restore a failed main car alarm unit, you usually need SMD installation skills and a soldering station. But in some cases it is quite possible to repair the alarm key fob yourself without special knowledge and tools. The same applies to minor software glitches in the operation of the security system and disruption of its connection with the antenna unit. A description of the main reasons for the lack of response of the alarm key fob to pressing buttons and ways to solve the problem is presented below.
Disabling or blocking. Most alarm key fobs can be disabled or blocked by pressing a specific combination of buttons. Before troubleshooting, check to see if the key fob has turned off and whether the protection against accidental button pressing has been activated .
Usually in this case, when you press the buttons, an inscription like “Block” and “Lock” appears on the screen, a symbol in the form of a lock appears, the car parameters are displayed or all the symbols light up, but nothing may happen. Combinations for unlocking and turning on/off the key fob for your security system model can be found on the manufacturer’s website or by calling the hotline, or try one of the ones listed below.
| Security system brand | Power On/Unlock Combination |
| Pandora, Pandect series D, X, DXL | Press and hold button 3 (F) for 3 seconds |
| Starline A63, A93, A96 | Simultaneously press buttons 2 (left arrow) and 4 (dot) |
| Starline A91 | Simultaneously press buttons 2 (open lock) and 3 (star) |
| Tomahawk TW 9010 and TZ 9010 | Simultaneously press the buttons with the “open lock” and “key” symbols |
| Alligator TD-350 | Sequentially pressing the “open trunk” and “F” buttons |
| SCHER-KHAN Magicar 7/9 | Simultaneously press buttons with symbols III and IV |
| CENTURION XP | Briefly press the button with the “open trunk” symbol, then press and hold for 2 seconds “closed lock” |
Oxidation of contacts after exposure to moisture, click to enlarge
Lack of power . If the alarm key fob stops responding to buttons, then the most common reason is a dead battery. In a situation where it is impossible to replace the battery, but you urgently need to open the doors and disarm the car, you can try removing the battery and lightly squeezing it in the center or simply knocking it on a hard object, such as a wheel rim. This will lead to the activation of chemical processes and the appearance of a charge, which will be enough for one operation.
Closing and oxidation of contacts . Often the alarm stops responding to the key fob after it gets caught in the rain or falls into a puddle. The cause of contact oxidation may also be electrolyte leaking from a worn-out battery. If the key fob gets wet, remove the battery as soon as possible, disassemble the case, and thoroughly dry the boards. The resulting oxides are removed using a soft toothbrush and a cotton swab or alcohol wipe soaked in alcohol.
Mechanical damage to buttons, cables and components . If the key fob body is strongly shaken, contact between its boards may be lost as a result of loosening and displacement of contacts or disconnection of cables. If the alarm key fob stops working after being dropped, you need to open the case and check the integrity of the boards, cables, and contact pads.
If there is no visible damage, try disconnecting and reconnecting the connectors. In cases where the alarm key fob does not respond to pressing individual buttons, special attention should be paid to them. You can check the functionality by connecting the tester probes in the dialing mode to the microswitch terminals and pressing the button.
Replacing worn buttons, click to enlarge
If there is no signal, it will have to be replaced. In this case, you will need a soldering iron, and the microswitch itself can be selected according to size in a radio parts store.
Software failure (key fob decoupling) . When installing an alarm system, the procedure for registering key fobs in the main unit of the security system is carried out. In the event of a software failure, errors in alarm settings, power failure, or a hacking attempt, initialization can be reset. In this case, all previously linked key fobs will be untied from the alarm.
In this case, the procedure must be carried out again using the Valet button, special software, connecting a PC or laptop with a cable to the connector in the main alarm unit or via a wireless channel (some modern models of security systems have this option).
The procedure for registering key fobs can be found in the instruction manual. Occasionally, a failure can be eliminated by rebooting the main unit, which can be done by removing the terminals from the battery for 20–30 seconds. If the alarm module is equipped with its own battery that provides autonomous power supply, this method will not help!
Fallen off alarm key fob antenna
Antenna malfunctions . The security system transceiver can be located inside the main alarm unit or in a separate housing. The latter is usually mounted on the windshield. If the remote antenna is mechanically damaged, the communication range with the key fob will drop significantly and it will only work in the immediate vicinity of the car or inside it. If the wire connecting the transmitter to the central unit is accidentally frayed or cut off, the main and additional key fobs will completely lose contact with the car.
The cause of a malfunction of the key fob may also be damage to its own antenna when dropped. Usually the antenna is made in the form of a spring and is soldered to the transceiver board. If the connection has deteriorated after the key fob has been dropped or hit, while the additional key fob is working correctly, you should disassemble the main remote control and check the condition of the connection between the antenna and the board and the contact of the transceiver with the second key fob board.
Why does it keep triggering for no reason?
One of the most common breakdowns of the security system is incorrect activation of the siren. This is usually caused by the shock sensor not working properly.
There are three options for sensor malfunction:
Constant operation due to unknown circumstances may be due to the increased sensitivity of the sensor. To bring the system back to normal, it is necessary to reduce the sensitivity. This can be done by turning the adjusting screw on the sensor body (there may also be a push-button adjustment). You can find out more about this in a special article on our website.
Incorrect installation also negatively affects the adequacy of the sensor. If it is poorly secured, then body vibrations are perceived incorrectly. Also, do not install it on plastic elements. The optimal location would be the engine shield.
If the sensor is adjusted and installed correctly, then most likely its hardware has failed. To eliminate errors in the operation of the security system, it will be necessary to repair or replace the element.
In some cases, a software error leads to such consequences. That is, the control unit erroneously gives an alarm. To resume proper operation of the security system, try resetting the system to factory settings. The algorithm for this procedure is clearly stated in the manufacturer's instructions. If this does not help, contact a specialized service center.
What to do if the alarm key fob does not respond to button presses
When you can’t open or lock your car with an alarm key fob near your home, first of all you need to try repeating the steps using a spare key fob and tag. Successful disarming of a car with their help indicates a malfunction of a specific remote control.
What to do if the alarm does not respond to the key fob: video
If the alarm does not respond to additional key fobs, or they are unavailable, and the quick troubleshooting methods described above do not help, several options are possible.
There are 3 ways to turn off the car alarm:
- deactivation by command from the phone (available only for models with a GSM module);
- secret Valet button;
- physical shutdown of the alarm unit.
Enabling and disabling security via GSM/GPRS module
Control of alarms and additional options via a mobile application
Suitable only for modern security systems equipped with a GSM/GPRS module. To disarm, you need to launch the application on your smartphone or submit a USSD command (for example, *0 for Pandora or 10 for StarLine), having previously dialed the number of the SIM card installed in the module. If the call is made from a phone that is not registered in the system as the main one, you will additionally need to enter the service code (usually 1111 or 1234 by default).
Similar actions can be performed using a mobile application from a linked device or from the security system website by logging into your personal account - to enter, use the login and password from the service card included in the alarm kit.
Emergency shutdown of the alarm with the Valet button
The presence of a "Valet" button in the alarm circuit helps control the alarm in case of emergency
To disarm the car, you need to get into the salon by opening the door with a key or an alternative method. You can turn off the siren that went off by having a snack and disconnecting one of the wires going to it under the hood, after first disconnecting the battery. If there are no alarms when the door is physically opened, you should check the battery charge - perhaps this is the problem.
The alarm is turned off by sequentially pressing the Valet service button in a certain sequence with the ignition on. The location of the Jack button and the combination will be individual for a specific alarm model (always in the manual for it).
Follow-up system check
Upon completion of the repair, you need to check the operation of the security system. To do this, activate the alarm and try to open the door or lightly hit the roof. After this, start the engine by opening the car doors with the key. After starting, the alarm should also go off. Other functions of the security system should also be checked. If everything works and the car alarm goes off, then this means that the repair work was successful.
Checking the car alarm for serviceability
Important! Driving a car with a disabled alarm is extremely risky, as it can be stolen or hacked. Therefore, at the first sign of a system malfunction, it is necessary to carry out diagnostics.
Troubleshooting
It’s quite simple to understand why the alarm system and control from the key fob are malfunctioning - there are not many breakdowns here, and they are all known:
If the steps taken are not successful, it is recommended to seek help from a specialist.
If the car alarm does not respond to the key fob
The anti-theft device may stop responding to commands from the control panel for several reasons:
Important! The key fob will not work for a trivial reason: you did not slam the car door, and there is no full contact between the surfaces.
Rebooting the alarm when the system hangs
Car alarms have their own software, which sometimes tends to freeze, after which the alarm stops responding to commands. Remove the terminal from the car battery, wait 5 minutes and return the terminal to its place. After power is applied and the system is turned on, the software should start correctly.
Attention! The siren may sound, but this is a normal reaction of the system.
Replacing fuses
Fuses often burn due to electrical overload and turn off the alarm. If you suspect that they are to blame, you should check the fuses:
The check is carried out visually or using a special tester.
Checking car alarm wiring
Electrical wiring should be left for last, and if you do not have the skills to repair electrical systems, it is better to contact the service center specialists. The system will be ringed at the stands, the damaged area will be determined, and then repaired or replaced.
Troubleshooting on the go
This is the most common problem in anti-theft systems, due to which you cannot put the car on the alarm, or remove it from the alarm to unlock the engine start.
First, check the batteries, then bring the key fob to the central unit of the alarm system and try to turn it on again. If it doesn’t start, the breakdown is serious and you need to contact a service station.
False alarm
If the alarm goes off spontaneously, it means that the battery in the car is dead, or the anti-theft device needs repair.
Causes of problems
High humidity
This factor can be attributed to unfavorable operating conditions of the vehicle.
Condensation, settling on contacts and electrical circuits, leads to short circuits that disrupt the operation of systems and lead to their failure. Humidity also greatly harms the alarm key fob. It is quite difficult to maintain and operate a car in a dry place due to rain if you do not have a garage. But the keychain is not only possible, but also must be stored in a dry place. This will extend its service life.
Problems with limit switches
If your alarm itself does not respond to the opening of the door or, on the contrary, it thinks that the door is open, but in fact it is not, then the problem is most often in the door limit switches. The limit switch is a button that is pressed by the door when it is closed. If it opens, the button is released and sends a corresponding signal to the control unit.
The limit switch may oxidize and become inoperable due to high humidity. If the wiring is shorted or the contact is lost, you can dismantle and clean them. But, since more and more often they are performed in conjunction with the door lock, this operation may not be simple.
Spontaneous change in sensor sensitivity level
This problem for sensors that are adjusted mechanically (with a screw or buttons on the body) can only be solved by replacing or repairing it. If the sensitivity level is set at the software level, then this may also be a failure in the algorithms of the alarm unit. In this case, you can also try resetting the settings to the original ones.
Attention! When performing the procedure for converting alarm parameters to factory values, strictly follow the instructions! Otherwise, your actions can disable or break the system. If you are not confident in your abilities, contact the dealer of the manufacturer of your complex.
Rattling of sensor contacts
Low or complete battery discharge and leakage in power circuits
As a rule, a low battery in a car is not dangerous for the alarm, but it does not allow the engine to start. If the minimum required voltage is lost on the power wires, the alarm will automatically turn off. The system turns off if the mains voltage drops below 8 volts. And after power is restored it will resume its work.
For a more correct procedure for waking up the system, we recommend that before starting the car after idle time with a discharged battery, remove the negative terminal from it for 2-3 minutes. During this time, the security complex will safely complete its work and reset its settings. After this, when you start the car, the alarm definitely won’t go off.
As for current leaks, they are most often caused by car alarms. Or rather errors in its installation. It's not that difficult to discover. To do this, you need to measure the leakage current first with the signal connected, and then turn it off. If in the second case the leak is less and is within acceptable values, it is necessary to check the correct connection of the system. This procedure can be performed at any dealer service center.
Electromagnetic interference
This often happens in big cities. Unlike other problems, this one is not caused by malfunctions of the security system or its elements. In order to disarm the car in the presence of interference, bring the key fob close to the antenna and press the key.
If the key fob still does not catch nearby, you can perform this procedure using the VALET button. To do this, open the car with the key and press Valet a number of times. For more information about this, see the instructions for the alarm or this article.
Unstable operation of the CAN bus
The CAN line is the main way to transfer information between vehicle systems. The performance of the car as a whole depends on it. Therefore, faults with CAN can appear in completely different and not obvious places. Most often, such problems are caused by an error in installing the alarm. In any case, such a problem must be dealt with by the service.
Volume sensor problems
This is also expressed in spontaneous alarm activations. The sensor can perceive people passing by as intruders. Such problems can be caused by two situations: improper installation and a malfunction of the sensor itself. For correct operation, the sensor must be installed approximately in the center of the car interior. For example, in the area of the parking brake lever. But if the sensor malfunctions, only replacing it will help.
Attackers
The most harmless situation is a “jammer” that interferes with the connection between the key fob and the unit.
For example, it can be used by a vindictive neighbor who is annoyed by the sound of your siren. But it’s worse when the equipment of car thieves creates interference with the system. If you arrive at the parking lot of a shopping center and observe unusual false behavior of the car alarm (for example, you cannot lock the car), it is better to park the car in another place. There is a high probability that the hijacker is trying to hack your alarm. If you need to park and get out of the car in this exact place, then quietly move away and watch it for a while. If the criminal has chosen your car as a target, he will try to approach your car as quickly as possible. Seeing this will help you stop him.
Tips and tricks
If any malfunction occurs in the operation of the car alarm, read the corresponding paragraph in the instructions from the manufacturer. It may be called “Faults and Possible Causes”. Having found your problem in the list, look at what solutions are described in the text.
And in any case, before starting use, read the instructions for use in full. An alarm system is a complex electronic system. It is not always possible to intuitively understand how to use it. And by exploring the capabilities of the system at random, you risk getting unpleasant consequences, such as completely disabling it.
It is better to install an alarm system in trusted services or dealer specialists are attracted by the low price of work. But often, behind such a price lies an unskilled worker and a disregard for work. The main criterion for choosing serious service centers or official dealers is the complete package of documents you receive after completing the work.
With these papers you can apply to them in a warranty case. But “garages” do not issue documents or receipts. If you complain about the quality of work performed, they may refuse to help you, and you will not be able to hold them accountable.
