Keyless Entry Systems Explained
A keyless entry system unlocks a car when it detects its own key close to the door, through a coded radio exchange between the car and the key, so no button is pressed and no blade is turned.
Inta-Lock Car Key Guides. Updated October 2026.
The car asks first and the key answers, and the doors unlock only for a key stored in the memory of the car. The same check runs again inside the cabin before the start button starts the engine. Remote, passive and digital systems share the name keyless entry, and each one unlocks and starts in its own way.
A flat fob battery does not leave a keyless car shut, because the fob carries a mechanical blade. A new key for a keyless car is cut and then programmed to the car, and the handbook of the vehicle states whether keyless entry switches off.
What Is a Keyless Entry System?
A keyless entry system is the part of the central locking that unlocks and locks a car by detecting its key nearby, instead of by a blade turned in a lock or a button pressed on the key.
The police describe it in one line in the Police.uk guidance on preventing vehicle theft. Cars with keyless entry unlock automatically when the key comes within a short distance of the car.
The key stays in a pocket or a bag. Car makers sell the system under their own trade names, and the handbook of the vehicle uses that name.
Keyless entry opens the doors. Keyless start is a second function that starts the engine from a button, and most cars with one carry the other. A car with a start button and a key that still needs a button press to unlock has keyless start without keyless entry.
How Does a Keyless Entry System Work?
A keyless entry system works by a short radio exchange in which the car calls for its key, the key answers with a coded reply, and the car unlocks once the reply matches a key stored in its memory.
- The driver touches or pulls a door handle, or presses the button on the handle. That contact wakes the keyless entry system.
- The car sends a short range radio signal from aerials at the doors. The signal is a question, and only a key close to that door receives it.
- The key fob answers with a coded radio reply that identifies it. The code changes with each use, so a recorded reply does not open the car a second time.
- The control unit of the car compares the reply with the keys stored in its memory. A match releases the door locks, and a key that is not stored gets no response.
- Inside the cabin the car repeats the exchange through its interior aerials. The start button starts the engine only while the key is detected inside the car.
Locking runs the same exchange in reverse. A touch on the handle sensor locks the car, or the car locks itself once the key has moved out of range, depending on the model.
How Do Remote, Passive and Digital Keyless Entry Differ?
Remote keyless entry unlocks on a button press, passive keyless entry unlocks on the presence of the key, and digital keyless entry replaces the key fob with a phone or a card that the car recognises.
| System | How the doors unlock | How the engine starts | Backup when the key fob battery is flat | What a new key involves |
|---|---|---|---|---|
| Remote keyless entry | A button on the key is pressed | The key blade turns in the ignition | The blade opens the door and starts the car | A blade cut, then the chip and the remote programmed |
| Keyless start without keyless entry | A button on the key is pressed | A start button, with the key inside the cabin | The blade in the fob opens the driver door, and the key starts the car from the backup position | A key fob programmed, and the emergency blade cut |
| Passive keyless entry and start | A door handle is touched with the key nearby | A start button, with the key inside the cabin | The blade in the fob opens the driver door, and the key starts the car from the backup position | A proximity key programmed, and the emergency blade cut |
| Digital key on a phone or a card | The phone or the card is brought to the door, on supported models | A start button, with the phone or the card inside the cabin | The key fob or the key card supplied with the car | Set up through the car maker for that model |
Passive keyless entry is the system most drivers mean by a keyless car. The table carries no figure for a new key, because a quote is agreed before work begins.
A keyless key that is lost, flat beyond a new battery or no longer recognised by the car is replaced by a key cut and programmed at the vehicle by Matt on supported vehicles.
Call Matt on 0116 442 2084What Happens When the Key Fob Battery Runs Flat?
A flat key fob battery stops the keyless functions and the remote buttons, and the car is then opened with the mechanical blade inside the fob and started from the backup position named in the handbook.
Most keyless fobs hold a metal blade behind a release catch. The blade fits the lock on the driver door, and turning the blade opens that door without any power in the key.
The car still reads a key held at close range. On some models the key is pressed directly against the start button, and other models carry a backup position for the key. The handbook of the vehicle shows the position for that model.
A new coin cell in the key fob restores keyless entry, and the handbook of the vehicle names the battery type.
A flat battery in the car itself is a different state. No door handle sensor works without vehicle power, and the blade in the driver door is the way in.
What Does a New Key for a Keyless Car Involve?
A new key for a keyless car involves a key fob of the correct type for the vehicle, an emergency blade cut to the door lock, and the fob programmed to the car so the keyless entry system accepts it.
A fob that has not been programmed gets no answer from the car, because the control unit only releases the locks for a key stored in its memory. Programming adds the new key to that memory, and the work is set out under car key programming, which covers keys, remotes and proximity fobs.
Identity and authority to request the work are checked before a key is made. The V5C vehicle registration certificate, which names the registered keeper, and photo identification are common examples, and what applies is confirmed on the call.
When a keyless key is lost or stolen, missing electronic keys are removed from the immobiliser memory where the vehicle supports it. A mechanical blade still turns a physical lock unless that lock is changed or rekeyed.
How Do You Tell Whether a Car Has Keyless Entry?
Four signs show that a car has keyless entry, and the door handle gives the clearest one.
- The door handle. A keyless door handle carries a small button, a ridged touch pad or a sensor area.
- The start button. A start button in place of an ignition barrel shows keyless start. Keyless entry is confirmed by the door test below, because some cars carry the button alone.
- The door test. A car with keyless entry unlocks when the handle is touched or pulled while the locked key stays in a pocket. A car without it stays locked until a button on the key is pressed.
- The handbook. The handbook of the vehicle lists the system under the trade name of the car maker, with the settings that belong to it.
Does Keyless Entry Switch Off?
Keyless entry switches off on some vehicles, either at the key fob or in the vehicle settings, and the handbook of the vehicle states whether the model allows it.
Some key fobs switch themselves off. Thatcham Research describes fobs with a motion sensor that detects when the fob has been stationary for a period and triggers a sleep mode, set out in its report on sleeping key fobs. A sleeping fob no longer responds until it is moved again.
Other fobs are switched off by hand. The advice from Thatcham Research on increasing car security is to refer to the user manual to see whether the fob deactivates at night.
With keyless entry off, the remote buttons and the blade still work the car. The button sequence differs between car makers, so the handbook is the source for each key.
What Else Is Linked to Keyless Entry?
Four questions sit beside the way a keyless entry system works, and each one belongs to a page of its own.
How Does a Flat Fob Battery Differ From a Keyless Fault?
A flat fob battery ends with a new coin cell, while a keyless fault stays after the battery is changed. With a fresh battery and a car that still does not detect the key, the cause sits in the fob or in the car.
Worn buttons, a cracked case, water inside the fob and a damaged circuit board are faults of the key itself, and that work belongs to key fob repair. A second key that works on the same car points to the first fob, and two keys that both fail point to the car.
Where Do Keyless Keys Sit Among Key Types?
A keyless key is one of several key types, and each type is cut and programmed in a different way. The guide to transponder, remote, smart and keyless keys sets them side by side with the signs that tell one from another.
How Do Relay Attacks Target Keyless Entry?
The exchange that makes keyless entry convenient is also the one thieves target. A relay attack fools the car into reading its key as close by. How the attack runs and what stops it are covered under relay attack prevention.
Why Does a Keyless Car Lock Itself?
Walk away locking and automatic relocking are keyless features, and both lock a car with nobody touching the key. The features and the faults behind the same behaviour are set out under why a car locks itself automatically.
A new or spare key for a keyless car in Leicester or Leicestershire starts with a call to Matt, and the phone is answered 24 hours a day.
Frequently Asked Questions
Is keyless entry the same as keyless start?
No, keyless entry unlocks the doors by detecting the key outside the car, while keyless start starts the engine from a button with the key detected inside the cabin.
Most cars with one function carry the other. Some cars carry a start button with a key that still unlocks on a button press.
Does a keyless car still have a physical key?
Yes, most keyless fobs carry a mechanical blade inside the case, and the car carries a door lock that the blade turns.
The handbook of the vehicle shows where the blade releases and where the lock is.
How close does the key have to be for keyless entry?
The key has to be within a short distance of the car, beside the door that is being opened, and the car maker sets that distance for each model.
A key left further away gets no signal from the car, so the doors stay locked.
Does a keyless car lock with the key inside?
Many keyless cars refuse to lock while the key is detected inside the cabin, and the handbook of the vehicle states how the model behaves.
The interior aerials that allow the engine to start also find a key left on a seat.
Does a phone work as a car key?
Yes, a phone works as a car key on supported models, where the car maker provides a digital key through its own app or account.
The car recognises the phone in place of the fob. The key fob or key card supplied with the car remains the backup.
Does keyless entry use the key fob battery?
Yes, a keyless fob uses its battery each time it answers the car, as well as each time a remote button is pressed.
A fob with a motion sensor sleeps while it is still.
How much does a replacement keyless key cost?
The cost of a replacement keyless key is quoted for the individual vehicle, and a quote is agreed before work begins.
The make, the model, the year and the key type all move the figure. A car with every key lost involves more work than a spare, which raises it. No price list is published.