Keyless entry lets you lock and unlock your car (or home) without inserting a traditional key. Depending on your system, you either press a button on a fob, touch the door handle while carrying the fob, or use a smartphone app. The exact steps vary by system type, so here’s how each one works and what you need to know to get the most out of it.
The Three Types of Keyless Entry
Not all keyless systems work the same way, and understanding which type you have determines how you’ll interact with it daily.
Button-press fobs (Remote Keyless Entry): You press a button on your key fob to lock or unlock the doors from a distance, typically up to about 100 meters. This is the most common system and has been standard on cars for decades. You may also be able to pop the trunk, trigger a panic alarm, or remote-start the engine depending on your vehicle.
Passive keyless entry: You don’t press any buttons at all. The car detects the fob in your pocket or bag as you approach, and the doors unlock when you touch or pull the handle. Walk away, and the car locks itself. This only works within about 2 meters of the vehicle for security reasons.
Smartphone digital keys: Newer vehicles let you use your phone as the key. The car communicates with your phone using Bluetooth or ultra-wideband (UWB) technology, which can pinpoint your phone’s location with centimeter-level accuracy. UWB measures distance based on timing rather than signal strength, making it harder to spoof. Some systems also support NFC, which works as a backup if your phone’s battery is low.
Using a Button-Press Fob
Hold the fob and press the lock or unlock button. Most fobs require one press to unlock the driver’s door and two presses to unlock all doors. The trunk release is usually a separate button, sometimes requiring a longer hold. Range varies by manufacturer, but you can generally expect it to work from across a parking lot.
To lock the car when you leave, press the lock button once. Many vehicles will honk or flash the lights to confirm. If you’re unsure the signal went through, press it again. Some fobs also have a remote start feature: press the lock button first, then hold the remote start button for a few seconds. The engine will run for a set period (usually 10 to 15 minutes) to heat or cool the cabin.
Using Passive Keyless Entry
If your car has passive keyless entry, you simply keep the fob on your person. As you walk up to the car, sensors in the door handles detect the fob’s signal. Touch the handle or press the button on it, and the door unlocks. Some vehicles also turn on approach lighting as you get close.
To start the car, sit in the driver’s seat and press the push-button start with your foot on the brake. The car verifies the fob is inside the cabin before allowing ignition. To lock up when you leave, turn off the engine, step out, and either touch a sensor on the exterior door handle or press a small button on it. The car confirms with a beep or light flash. Walk away, and many models will auto-lock after a few seconds once the fob is out of range.
Setting Up a Smartphone Key
If your vehicle supports digital keys, you’ll typically set it up through the manufacturer’s app (BMW Digital Key, Hyundai Digital Key, etc.) or through your phone’s built-in wallet app. The process usually involves pairing your phone to the car via Bluetooth while sitting inside the vehicle, then following on-screen prompts to register your device.
Once configured, your phone works like a passive fob. Approach the car, touch the handle, and it unlocks. Place the phone on the wireless charging pad or designated spot inside, and you can start the engine. One advantage of digital keys is the ability to share access with someone else by sending them a virtual key through the app, often with restrictions like limiting top speed or access hours.
Keyless Entry for Your Home
Home keyless entry systems work on similar principles but offer more authentication options. The most common types include keypads, where you punch in a numeric code on the lock itself. Smart locks add app-based control, letting you lock and unlock your door from anywhere with your phone. Some detect your phone’s proximity automatically and unlock as you approach, similar to passive car entry.
Biometric locks use your fingerprint, facial recognition, or even a retinal scan. These are the fastest to use since you just touch the sensor, but they tend to cost more. Most smart locks let you set up multiple methods at once, so you might use your fingerprint day to day and share a temporary PIN code with a houseguest.
What to Do When the Fob Battery Dies
A fob battery typically lasts 2 to 5 years depending on how frequently you use it, since each button press or passive detection transmits a radio signal that draws power. You’ll notice the range shrinking or the car taking multiple attempts to respond before the battery dies completely.
When it does die, you’re not locked out. Nearly every modern fob has a hidden physical key blade inside it. Look for a small slider or button on the side of the fob, release the blade, and use it on the driver’s door. The keyhole is sometimes concealed under a small cap on the door handle.
To start the car with a dead fob, try holding the fob directly against the push-button start or a marked spot on the steering column. The car can read the fob’s internal chip through short-range induction, even without battery power. Some Honda and Hyundai models have a backup slot in the glove box or center console where you insert the fob directly. BMW and Mercedes often include a dedicated fob slot hidden under the dash or in the center console.
Replacing the battery is straightforward. Most fobs use a CR2032 coin cell. Pry the fob open with a coin or small flathead screwdriver, swap the battery (note the orientation), and snap it back together. A fresh CR2032 should read close to 3 volts. If it reads below 2.8 volts on a multimeter, it needs replacing.
Keeping Your Keyless Entry Secure
Keyless systems use rolling codes, meaning the fob generates a new encrypted code every time you press the button. Your car won’t respond to a previously used code, which prevents someone from recording your signal and replaying it later.
The bigger vulnerability is the relay attack, which targets passive keyless entry specifically. Two thieves work together: one stands near your car with a device that captures the car’s signal, while the other stands near your house (or wherever you are) with a device that picks up the fob’s response. They relay the signals between the two devices, tricking the car into thinking the fob is right next to it. This can happen through walls, so a fob sitting on your kitchen counter near the front door is an easy target.
The simplest defense is a Faraday pouch, a small bag lined with signal-blocking material that costs a few dollars. Drop your fob in it when you’re at home or not using the car, and the signal can’t be captured. Some newer fobs include built-in motion sensors that put the fob to sleep after being stationary for a few minutes, which also defeats relay attacks. Check your owner’s manual to see if your fob has this feature or if it can be enabled through the vehicle’s settings.
Storing your fob away from exterior walls and doors adds another layer of protection. If a thief’s relay device can’t pick up the fob’s signal from outside your home, the attack fails.