Why Does My Key Fob Not Work After Replacing Battery?

Modern key fobs are an essential part of today’s cars, providing drivers with quick and easy access to their vehicles. These small, handheld devices typically consist of a keypad or buttons that can be used to lock and unlock the car doors and start the engine with a simple push of a button.

Not only do key fobs make it easier and more convenient to drive your car, but they also offer increased security and protection against theft. Many modern key fobs come equipped with sophisticated anti-theft features such as remote locking and GPS tracking, helping you stay in control of your vehicle at all times. Whether for added convenience and security or upgrading your current car keys, modern key fobs are the perfect solution for any driver.

key fob example

Why Does My Key Fob Not Work After Replacing Battery?

Usually, the key fob is not working after the battery change because the key fob is not reset. To fix the problem, do the following steps:

  • Replace the batteries inside the key fobs.
  • Take the key fob apart and check for broken contacts or misaligned buttons.
  • Get Inside the Car.
  • Turn on the Ignition.
  • Press the Lock Button on Remote.
  • Listen for a Lock Sound.
  • Programming Additional Remotes.
  • Turn Off the Ignition.
  • Step out of your car and test the result.

You can see how to check our article where we describe Steps to Reset Key Fob for different car brands.

Key fobs are small electronic devices that allow you to remotely control certain functions of your car, such as unlocking the doors or starting the engine. If your key fob suddenly stops working after replacing its battery, it may be due to several factors.

Here are some possible reasons why your key fob might not be working after replacing its battery:

  • You need to reset the key fob in your car. (See steps above)
  • The new battery may not be fully charged or properly installed. Many key fob batteries will only work if fully charged and correctly inserted into the device. If your new battery isn’t working properly, try charging it for a few hours before trying again.
  •  There could be an issue with connecting your key fob and the car itself. This is especially common if you’ve recently had other repairs done to your vehicles, such as a new ignition switch or a replacement for a faulty wiring system. Ensure that all cables and connectors in your car are securely connected to the key fob and that there is no corrosion on these components that could affect their performance.
  • There may be something interfering with the signal from your key fob to your car’s computer system. For example, suppose you keep electronics or other devices close to your car keys. In that case, this can cause interference that interferes with the signal between the two devices and prevent them from communicating effectively. Try moving any nearby objects away from your keys to see if this helps restore functionality to your key fob.

Suppose none of these solutions help resolve the issue, and you continue to experience problems with your key fob after replacing its battery. In that case, it may be time to bring your vehicle to a mechanic for further diagnosis and repair services. In most cases, issues with a key fob can be resolved relatively quickly and easily by addressing any underlying causes for not working as expected.

To repair the key fob, see the video below:

Security is a big concern for car owners despite the default security system of the car. The traditional concept of locks and keys has been eradicated, and the impression of keyless and remote locks is no longer dominating the automobile industry. Nowadays, state-of-the-art vehicles are equipped with an electronic authorization system available to car owners as part of the manufacturing process or added as an extra option. The smart key was first used by the Siemens Company in 1995 and was assigned to Mercedes-Benz.

The smart electronic key operates by keeping the key fob close to the driver during unlocking and locking the car. Specific antennas are fortified in the car’s interior structure and bodywork. The smart key derives its signal along with the radio pulse generator strengthened in the robust housing. Automobile companies and car manufacturers have a different mechanisms of the key system. Vehicles set by the smart key system at the time of manufacturing have a mechanical backup in the shape of a spare key blade partnered with the vehicle.

The electronic authorization access system is convenient for quick locking and unlocking cars; however, it can be challenging. The smart key or key fobs are mainly responsible for controlling the car’s doors and trunk alarm system, allowing drivers to unlock or start the vehicle from a certain distance. These electronic systems function similarly to other electronic items; therefore, they possess their chances of malfunctioning after using them for a while. The electronic malfunction may relate to signal loss; however, you can reprogram the remote yourself.

To save time and money, drivers can repair the car key fob to avoid taking the car and the system to the auto dealer. Different manufacturers and car production companies fortify and program their vehicles through other mechanisms. Because of varying car mechanisms, the process of re-programming the key fobs is diverse and contradictory, which can be understood by going through the car’s manual. The first step is removing and accessing the key fob’s old batteries. If the key fob cannot perform its function, then the old batteries are highly likely to require replacement. If you have not had the chance to replace the original batteries after a while, you may take this opportunity to insert fresh batteries by going through the owner’s manuals.

If replacing the batteries has not helped in properly functioning the car key, sit in the driver seat with the electronic remote and close all the doors properly. Turn on the ignition which will automatically give electrical power to the car. The ignition should not be on radio mode and not start the engine. After turning on the ignition, press the lock button on the remote key. While performing this step, the key should be in the on position. Press the keys lock button and rotate it to the off position; repeat this process thrice. This action will help save the data as the ignition will send direct signals to the electronic control unit. Repeat this process three times, and you will hear the lock sounds from the car’s locking system. This means that you have entered the programming mode. Once you have reached the programming mode, press the lock button to fulfill their programming. Before turning off the ignition, try stimulating additional remotes by pressing the lock button for at least 10 seconds. Lastly, come out of the car and experiment with your key fobs by locking and unlocking the doors.

If the key fobs cannot function, then take assistance from specialist hardware experts who will re-encode the car remotely. If you are interested in programming the new key fob without specialized help, you would require appropriate tools. As far as the cost is concerned, reprogramming will cost you nothing if you follow basic guidelines from the manual; however, if you need to reprogram the immobilizer function, you can expect to spend $200-$500 for professional help.

Key Fob is now a significant aspect of access control and car security systems. Key fobs work on the concept of RFID technology which is novel, efficient, and secure in programming. The key fob revolves around keyless access strategies and derives energy from the short-range radio transmitter.

The transmitter stimulates and senses a coded signal to the receiver unit when the driver pushes the fob. Most car manufacturing companies equip their cars with a push-button start system, keyless strategy, or even a combination. These key fobs are highly convenient for drivers but can add to the expense if lost or broken.


Several possible reasons why your key fob may not work after replacing the battery. Usually, you need to reset the key fob from your car, and the problem will be fixed. However,  some problems include issues with the battery itself, problems with the electrical contacts in the fob, or even damage to the fob’s programming chip. To troubleshoot this issue, it may be helpful to consult the user manual for your specific model of the key fob or to contact a professional locksmith for assistance. Ultimately, if you cannot resolve the problem alone, you may need to purchase a replacement key fob to regain access to your vehicle.


Robert Aksamit

Robert Aksamit

Robert Aksamit is a mechanical engineer and automotive industry expert. Robert was born in Minnesota and worked in the US automotive industry for 25 years. He is highly regarded for his passion and dedication to continually improving vehicles in response to customer feedback. Robert has a keen eye for sourcing the best vehicle components and materials on the market and is always looking for ways to enhance the user experience. As a writer, Robert covers automotive-related topics. Read more on Robert Aksamit's about page. Contact Robert: robert@promtengine.com

Recent Posts