Car won’t unlock via key remote – how to troubleshoot

The vast majority of modern cars are not only equipped with central locking, but also with a standard alarm. There are a variety of models of these security systems. However, the main problem they all face in their life is the same: they don’t want to respond to commands from the key remote. How can you fix the problem quickly?

The first thing a person does when something goes wrong in their hands is to shake and hit the problem to resolve the problem. Surprisingly, it helps sometimes. However, with high price of replacement car key, it is better not to use this method at all.

First of all, you need to find out why the device does not respond when you press a button on the remote control. Here are the main reasons:

  • Dead key fob battery;
  • Dirt or oxidation inside key fob hindering electricity flow;
  • Radio interference;
  • Wear and tear of the security system;
  • The car battery is dead;
  • Electronics failure.

Key fob battery is dead

This is the most common problem with electronic devices with mobile remote control. The easiest way to identify the problem is to use the vehicle’s additional remote control. They often come with a control unit. When the spare key opens the car, it’s time to change the battery in the master key fob.

Replacing battery on 2009 Honda Civic key fob – (photo by WheelsJoint)

When a battery runs out of capacity, it usually affects the range of the keychain. If the car responds to the signal at a shorter distance each time, then you need to look for a suitable battery. And you can’t buy them in every store.

Note: Key fobs commonly use CR2025 or CR2032 batteries, although CR1620, CR1632, and others are also used in some applications.

Contact failure

Oxidation of contacts is a common cause of poor signal transmission. Most often this problem occurs in the battery compartment of the key fob. The malfunction can be remedied by simply cleaning the contacts.

Dissembled key fob of Honda Civic for thorough cleaning

Otherwise, the vehicle may send incorrect data to the control panel. A loss of signal on a rusty door or on a bonnet contact is recognized by the anti-theft system as an attempt to break into the car. If the key fob shows the arming zone, the problem is easier to fix. Otherwise, you need to check all connections in the anti-theft device.

Vehicle is in a radio interference zone

If the key remote suddenly stops working after the car is parked near a safe facility, the cause of the malfunction is radio interference. This problem can also be observed in large parking lots in large cities.

If the driver cannot arm the car, find another parking space. Some anti-theft systems are equipped with automatic activation. In this case, you must bring the key fob as close as possible to the antenna module to switch off the signaling.

Wear and tear of the alarm system

Long-term operation of a device inevitably leads to its failure. In the case of vehicle safety, the key fob’s signal quality gradually decreases. Sometimes the problem is with the antenna.

Incorrect installation of the transmitter module can also affect the quality of the transmitted signal. It must be installed at a minimum distance of 5 cm from the metal parts.

Car battery is dead

Modern cars have more and more electronic comfort and safety systems, which places special demands on the car battery. In the case of a low battery, it may be the reason the car does not respond to the remote key.

To open a “sleeping” car, simply use the key on the door. If the problem occurs in winter, you need to diagnose the battery.

Healthy car battery should have 12.4 to 12.7 volts

You can measure the voltage of the battery yourself with a standard multimeter. To do this, connect the red cable of the multimeter to the positive pole of the battery and the black cable to the negative pole. After not driving the car for a few hours, the voltage should still be between 12.4 and 12.7 volts. If the voltage is less than 12 volts, the battery should be recharged or replaced.

Electronics failure

Old wiring is another cause of signaling problems. Because of this, they can occur frequently and unexpectedly. It is impossible to say for sure in which node contact is lost. To do this, you need to test all of the wires. Without the right skills, this problem cannot be solved. Therefore, it is better to take the car to an electrician.

If the alarm behaves strangely (it restarts for no reason, executes commands incorrectly), this is a symptom of a malfunction in the control unit. In this case, you also need to show the car to a specialist. You may need to flash your device again.

The problem with door mechanics

Another problem can arise in winter. The control panel indicates that the central locking system is open, but it is not. Do not think that this is an alarm nuisance. The first thing to do is to check whether the door mechanisms are rusted or not.

It wouldn’t hurt to test that the central locking itself was working either. If there is no sound when you press the opening button, you should check the fuses or cables.

Sensor malfunction

In modern automobiles, anti-theft systems are linked to car sensors. The more complex this circuit, the higher the probability of failure. The reason is either that the contact is oxidized or the sensor is not operating.

Do not rush to change the sensor immediately. First, try cleaning the cable connection.

Water damage

Although car key fobs are water resistant, but they are not completely waterproof. Check if there is any water damage on the circuit board of the key fob. If there is such damage, you may have to buy a new key remote for your vehicle.

Author: Nabeel K


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1 year ago

If it’s a toyota they don’t know why their key fobs quit working. My 2007 Avalon’s key fob quit working 4-5 years ago. They worked on my car and could never find the problem. They gave me the option of putting a new CPU in which was 1000 bucks at the time but wouldn’t guarantee that would fix the problem. As an aside, the technician had the same year and model and said his is the same way.

Also, my daughter had a 2012 Camry and encountered the same problem at about 5 years. Toyota claims there isn’t a problem with their products. I’ve owned Toyotas since 1987, but will never buy another one because of this unresolved problem. They won’t take responsibility.

1 year ago

I have a 2011 F150. About two yrs ago, my keyless entry stopped opening my truck. It would still lock the truck and set the alarm, but just wouldn’t unlock it. I replaced the battery immediately but it continued to do the same thing. So I switched to my other remote and used it for the past two yrs. Now that remote is doing the same thing. Any idea what I should do to fix this problem?

Stuart T
Stuart T
7 months ago
Reply to  Anonymous

Change the battery