What Is a Key Fob?

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What Is a Key Fob?

A remote-entry key fob is not your average keychain accessory. These small plastic controllers are a big convenience for car owners. Key fobs are an integral component of a keyless entry system. Locking and unlocking a car with a key fob is as easy as pushing a button. Some cars come equipped with a keyless entry system designed by the manufacturer. In this case, the buyer receives a keychain controller along with the keys to the new car. When a used car does not include a key fob, buyers can check to see if their model already has the proper wiring. If so, replacement key fobs might be available.

Custom installation of a remote-entry system allows consumers to choose additional key fob features. This guide describes how key fobs work while highlighting their varied benefits. Installation, replacement, and repair tips are included as well. Key fobs can be purchased through car dealerships, aftermarket accessory shops, and automotive locksmiths. Replacement fobs and keyless entry systems are also sold by many Internet merchants, along with online auction sites like eBay Motors.

Key Fob Definition

A key fob is a palm-sized portable device capable of controlling various parts of a car. Their primary function is to manage the remote-entry system installed in a car. Design dictates whether the controller stands alone or works like a keyring. Depending on the style, the fob may also include a regular or valet key for the vehicle. Aside from locking and unlocking car doors, some key fobs can:

  • Pop the trunk latch
  • Remotely start the vehicle ignition
  • Arm/disarm a security system
  • Activate the panic alarm
  • Control automatic windows

The Benefits of Key Fobs and Remote Entry

After trying a keyless entry remote, unlocking a car the old-fashioned way feels like a chore. Keychain controllers make life easier, and they can even help people stay safe. Those who do not currently have a keyless entry system can opt to install a custom model with a personalized array of benefits. Key fob covers and jackets allow people to add a bit of flare to remote entry devices in standard shapes.


Many automakers include remote entry as a standard feature on all cars with electronic locks. Rather than digging their keys out from a purse or pocket, remote fob users control their car with the touch of a button. Some fobs, known as smart keys, automatically unlock the doors when in close proximity to the car. Certain situations, like carrying armfuls of groceries or a child, make it difficult to unlock a car with ease. With remote entry, drivers have almost immediate access to the inside of their car.


Though drivers hope they never have to use it, most key fobs feature a panic button for personal safety. When this button is pressed, the car alarm is triggered, causing the horn to honk and the lights to flash. In the event of an assault or carjacking, this is a potentially life-saving feature. The combination of noise and lights is likely to scare off the perpetrator. It may also catch the attention of people that can help. Some key fobs offer additional features aimed at keeping drivers safe. These might be as simple as dome light controls or as sophisticated as a sensor that detects the presence of a human heartbeat.

Customizable Options

By installing a custom keyless entry system, consumers have greater control over fob features. High-end key fobs are often synced to remote car starters and sophisticated vehicle security systems. Some designs include an LCD screen with advanced vehicle monitoring capabilities. Undesignated auxiliary buttons on a key fob make it possible for drivers to control various accessories remotely. Tech-savvy individuals might be capable of wiring a keyless entry kit themselves. Alternatively, many prefer to leave installation to the professionals at car accessory shops and authorized dealerships.

How a Key Fob Works

Though they may not look like much, key fobs utilize fairly sophisticated radio technology. Every manufacturer’s keyless system is a bit different, but they all work in a similar way. Within the plastic shell of the keychain controller lies a tiny circuit board with a radio transmitter and control chip. Key fobs work like garage door openers, but with advanced security features to prevent code capturing. When the driver hits the button to unlock the doors, the fob sends a code and a command to the receiver in the car. If the transmission matches the code in the receiver’s memory, the command is carried out.

Key Fob Security

Key fobs are designed to unlock only the car they are synchronized with. The hopping or rolling code technology embedded in the fob provides a high level of security. It also keeps people from unlocking the doors of others accidentally in a crowded parking lot. Each time the driver presses a button on the fob, another code is generated by the transmitter and the receiver. With trillions of possible combinations, predicting key fob transmission codes is next to impossible. This means it is unlikely that a would-be car thief could break into a car by intercepting or hacking the keyless system.

Key Fob Replacement and Repair

If a keyless remote is lost or broken, compatible replacements are not hard to find. After purchasing replacement fobs, they must be programmed for use with a specific car. By learning how to replace the batteries in a key fob, consumers can sometimes avoid spending money on a new device.

Locating a Replacement Key Fob

Before buying a new or used key fob, it is important to determine compatibility. Replacement remotes for factory-installed systems are easy to come by, but in many cases, they only work on certain cars. Browsing by make and model is the fastest way to find a compatible fob. Those with a custom keyless system are generally able to find replacements key fobs for their cars too. In this situation, the buyer may want to contact the system manufacturer or the individual that installed it. Both factory and aftermarket fobs can also be found online and in many automotive parts and accessories stores.

How to Program a Key Fob

After determining compatibility and buying a new fob, the next step is programming it. Certain factory-installed fobs can only be programmed by an authorized dealer. If consumers are able to do it themselves, instructions are usually included with the fob. In a pinch, manufacturer-specific programming instructions are often available online. Thankfully, once a keyless remote is programmed for a particular car, it should stay that way indefinitely. If a key fob suddenly stops functioning properly, most likely the batteries are to blame.

How to Change the Batteries in a Key Fob

If a key fob seems sluggish or stops working entirely, the batteries are usually the problem. Luckily, some remote fob designs allow the owner to easily change them. If so, instructions and compatible battery types are often listed in the owner’s manual. If key fob replacement batteries are available, there may be no need to buy a new fob. After changing the batteries, the outer shell is put back together, leaving the keychain controller as good as new. There should be no need to reprogram the device.

How to Buy a Key Fob on eBay Motors

By searching Parts & Accessories on eBay Motors, you can find replacement key fobs and keyless entry installation kits. To browse a wide selection of items, input the words "key fobs" or "keyless remotes" into the main search box on the eBay Motors homepage. This approach may produce too many results to scan quickly. If so, narrow down your results list with available refinements such as price or condition. To conduct a more efficient search, look for fobs compatible with your make of car. You can find key fobs for GM, Chrysler, Toyota, Nissan, and many other makes of car on eBay Motors. To compare your options, add items to your watch list. By doing so, you can easily return to listings you are interested in.

Check Key Fob Compatibility

If you plan to buy a key fob on eBay Motors, always research the item first. To find out if a particular replacement remote is compatible with your car, visit the listing page. Look for the chart identifying compatible makes and models, and then input your vehicle information to check for a match. While evaluating potential keychain controllers, don't forgot to look for programming instructions as well.


A key fob is a nifty electronic device designed to control a vehicle’s keyless entry system. With a fob, drivers can unlock their car doors remotely from a distance. Many keychain controllers also include a trunk release for added convenience and a panic button for personal safety. Sophisticated remote-entry security systems might include a fob capable of remotely starting the car. Additionally, auxiliary buttons on fancy fobs offer customizable functionality for consumers. To enjoy the benefits of a keychain controller, a car must have a factory-installed or aftermarket remote-entry system. Almost any car with power locks is a candidate for a keyless entry installation.

If a key fob is missing or damaged, replacements are often available. eBay Motors offers a large selection of key fobs and remote-entry installation kits for shoppers to consider. Sometimes, a broken fob simply needs new batteries to work properly again. Before buying a new fob, it is imperative that consumers check vehicle compatibility. After finding a suitable keyless remote, the device must then be synchronized with the car according to the manufacturer’s instructions. Some key fobs are easy to program at home, while others require help from an authorized dealer.

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