What is Key Fob? - Okey DoKey Locksmith
A car key fob is a small electronic device used to communicate wirelessly with a vehicle. Depending on the vehicle and type of fob, it may lock and unlock the doors, open the trunk, activate the panic alarm, remotely start the engine, or allow keyless entry and push-button starting.
The term "key fob" covers several different automotive devices. Some fobs are separate remotes used alongside a traditional ignition key. Others are built into a remote-head key, while newer vehicles may use a smart or proximity fob that can remain in your pocket while you unlock and start the vehicle.
Because key fobs contain electronics, replacing one can involve more than simply cutting a new key. The replacement must be compatible with the vehicle, and it may need key fob programming before the vehicle will recognize it.
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What Is a Key Fob?
A key fob is an electronic transmitter that communicates with a receiver installed in the vehicle. Pressing a button on a conventional remote fob sends a wireless signal telling the vehicle to perform a particular function.
For example, pressing the unlock button sends an electronic command to the vehicle. If the vehicle recognizes the transmission as belonging to an authorized fob, it performs the requested function.
A key fob does not necessarily replace the physical car key. On some vehicles, the fob is simply a remote control used alongside a separate mechanical or transponder key. On others, the blade and remote are combined into a single unit.
Types of Car Key Fobs
The meaning of "key fob" has expanded as automotive key technology has changed. Several different types are commonly encountered.
Separate Remote Fob
Older remote keyless-entry systems may use a small remote key fob attached to the same key ring as a separate ignition key. The fob controls functions such as locking and unlocking, while the physical key operates the ignition.
Remote-Head Key
A remote-head key combines the blade and remote buttons into one housing. Many also contain a transponder chip used by the vehicle's immobilizer.
That means a single key can contain three different systems: the blade that operates the mechanical lock, the transponder used to authorize engine starting, and the remote transmitter used for functions such as locking and unlocking.
Flip Key
A flip key has a mechanical blade that folds into the remote housing when it is not being used. Pressing a release allows the blade to swing outward for use in the ignition or door lock.
FOBIK-Style Key
Some vehicles use an electronic key design that is inserted into an ignition module rather than using a conventional exposed metal ignition blade. These systems should not be confused with every other type of key fob simply because the word "fob" appears in the name.
Smart / Proximity Key Fob
A smart or proximity key can communicate with the vehicle without requiring the driver to press a button for every operation. On equipped vehicles, the doors may unlock when an authorized fob is nearby, and the engine can be started with a push button while the fob remains in the driver's pocket or bag.
What Does a Key Fob Do?
The available functions depend on the vehicle and its equipment. A key fob may be used to:
- Lock and unlock the doors
- Open or release the trunk
- Activate the panic alarm
- Arm or disarm the vehicle security system
- Operate a remote-start system
- Control certain power doors or other equipped features
Not every fob supports all of these functions. The buttons and capabilities are determined by the vehicle and keyless-entry system.
How Does a Key Fob Work?
Inside a typical key fob is a small electronic circuit containing the components needed to transmit information to the vehicle. When a button is pressed, the fob sends a radio-frequency transmission containing information the vehicle uses to determine whether the command came from an authorized remote.
The vehicle contains a receiver. When it receives and recognizes the transmission, it can perform the requested operation, such as unlocking the doors or releasing the trunk.
Modern remote systems incorporate security measures intended to prevent a simple recording of one transmission from functioning as a reusable copy of the remote command.
Key Fob vs. Smart Key
A conventional remote key fob and a smart key are related technologies, but they do not operate in exactly the same way.
With a traditional remote-entry fob, you normally press a button to lock or unlock the vehicle. The remote sends the requested command to the vehicle.
With a proximity or smart-key system, the vehicle can detect an authorized fob nearby. Depending on the vehicle, touching the door handle may unlock the door without pressing the fob's unlock button. The same proximity system can allow push-button starting while the authorized key remains inside the vehicle.
Many smart keys still include ordinary lock, unlock, trunk, and panic buttons, so a modern smart key is also commonly referred to as a key fob.
Key Fob Security
Automotive remote systems are designed so that another driver's fob cannot simply unlock your vehicle because it transmits on a similar radio frequency.
The vehicle and authorized fob use electronic identification and security protocols to determine whether a received command should be accepted. The exact system varies by manufacturer and vehicle generation.
The security technology used in keyless-entry systems has also evolved over time. Older and newer vehicles should therefore not be assumed to use the same type of remote communication or protection.
Common Key Fob Problems
If a key fob stops working properly, the fob itself is not necessarily completely defective. Common symptoms include reduced operating range, buttons that respond intermittently, damaged buttons or housing, and a remote that no longer communicates with the vehicle.
Possible causes include a weak battery, physical damage, worn button contacts, electronic failure, or a problem involving the vehicle rather than the remote.
If you have a second working fob, comparing the two can help determine whether the problem appears to be isolated to one remote.
Key Fob Battery Replacement
A weak battery is one of the first things to consider when a previously working remote develops reduced range or intermittent operation.
Many fobs use a replaceable coin-cell battery. The required battery and opening procedure depend on the fob design, so check the vehicle owner's manual or applicable instructions before opening the housing.
When replacing the battery, note its type and orientation before removing it. Avoid damaging the circuit board, battery contacts, buttons, or housing while the fob is open.
A simple battery replacement generally does not mean that an otherwise functioning fob needs to be replaced.
Key Fob Replacement
If your remote is lost or damaged beyond repair, a replacement key fob must be compatible with your particular vehicle and key system.
Do not rely only on physical appearance. Two remotes can have identical buttons and housings while using different electronics. Depending on the vehicle, identifying information such as the part number or FCC ID can help determine compatibility.
Replacement fobs can be obtained from automotive locksmiths, vehicle dealerships, automotive key suppliers, and online sellers. See our buy keys online guide for additional options.
If the fob is incorporated into a physical car key, replacement may also require car key replacement services such as blade cutting or transponder programming.
Key Fob Programming
A compatible replacement fob normally has to be associated with the correct vehicle before its remote functions will operate. This process is commonly referred to as key fob programming.
The programming procedure varies by manufacturer, model, year, and key system. Some vehicles may support an onboard procedure under particular conditions, while others require compatible diagnostic or key-programming equipment.
Remote programming should also not automatically be confused with transponder programming. On keys containing both systems, the immobilizer transponder and remote-entry functions may involve different procedures.
An automotive locksmith or vehicle dealership may be able to program a compatible replacement fob when specialized equipment is required.
What If Your Key Fob Is Lost?
If you lose a key fob but still have another working key, making a replacement before the remaining key is also lost can prevent a more complicated all keys lost situation.
If every working key or fob has been lost, a replacement may still be possible. The procedure depends on the vehicle's key system and can involve identifying the correct key, cutting a mechanical or emergency blade when applicable, and programming the new electronic key to the vehicle.
For security, a lost electronic key may also need to be addressed as part of the vehicle's authorized-key configuration, depending on the system and available programming procedure.
Key Fob FAQ
Is a key fob the same as a car key?
Not always. A fob can be a separate remote used alongside a mechanical key, part of a remote-head key, or a smart key that performs both entry and starting functions.
Does every key fob contain a transponder?
No. A remote-entry fob and an immobilizer transponder perform different functions. Some modern keys contain both technologies in the same housing, while separate remote fobs may only control remote-entry functions.
Can I buy a replacement key fob online?
Yes, compatible replacement fobs are available online. Verify the vehicle application and relevant identifying information before ordering. See where to buy car keys online for more information.
Does a new key fob need to be programmed?
A replacement electronic fob generally must be associated with the intended vehicle. How this is done depends on the vehicle and key system.
Will changing the battery erase the key fob?
Replacing a weak battery in an otherwise functioning fob normally addresses the power source rather than replacing the electronic identity of the remote. Follow the appropriate battery replacement procedure for the particular fob.
Can a locksmith replace a key fob?
An automotive locksmith with compatible equipment may be able to supply and program replacement fobs and, when applicable, cut the associated mechanical key blade.
