Car Key Replacement Guide, How a Car Key Is Replaced
Car key replacement works in five stages, the key type is identified, the cuts are sourced, the blade is cut, the new key is programmed to the car, and missing keys are removed from the immobiliser memory.
Inta-Lock Car Key Guides. Updated October 2026.
A car key is replaced when it is lost, stolen, broken or worn, or when a spare is wanted. The situation decides the stage at which the work starts, and the table below maps six situations to that stage. A replacement key carries up to three parts, a blade, a transponder chip and a remote.
This guide gives the short answer on the stages, the two routes, what to have ready, what decides the cost and the time, and what happens to the old key. No price and no duration is printed here. A quote is agreed before work begins.
How Does Car Key Replacement Work?
Car key replacement works by making a new key that matches the car in two ways, a blade cut to the locks and electronics programmed to the immobiliser, in five stages from identification to the removal of missing keys.
A car key is the device that opens the doors of a vehicle and starts its engine. On a car with an immobiliser the blade turns the locks, and a coded chip tells the car that the key belongs to it. Immobilisers prevent a vehicle from starting unless the correct fob, key or activation process is used, as the police guidance on preventing vehicle theft states.
So a replacement is two matches and not one. A blade that fits the locks opens the door, and a key that the immobiliser recognises starts the engine.
What differs from one replacement to the next is the starting point, and the situation behind the replacement key decides it.
Which Situations Lead to a Replacement Car Key?
Six situations lead to a replacement car key, a spare wanted, a worn key, a broken key, one key lost, every key lost and a stolen key, and each one starts the work at a different stage.
| Situation | Keys still held | Where the work starts | What the situation adds |
|---|---|---|---|
| A spare key is wanted | One working key or more | Stage one, with a working key to identify and to copy | Nothing. The car drives throughout |
| The key is worn | One key that still works with effort | Stage two, the source of the cuts is chosen before a worn blade is copied | The question of whether the wear sits in the key or in the lock |
| The key is broken | The pieces of the key, and a second key in some cases | Stage one, with the pieces of the key as the pattern | Extraction first where a piece of the blade sits in a lock |
| One key is lost and one is left | One working key | Stage one, with the working key to identify and to copy | Removal of the lost key from the immobiliser memory where the vehicle supports it |
| Every key is lost | No key | Entry to the car, then stage one with no key to copy | Cuts sourced with no pattern, and the same removal of the lost keys |
| The key is stolen | One key or no key | The same stage as a lost key with the same keys held | A report to the police, the same removal of the stolen key, and a decision on the locks |
The keys still held decide where a replacement key starts. A theft is reported to the police as well. Theft is among the incidents the police take as an online report, and 101 is the number for non emergency enquiries.
What Does a Replacement Car Key Consist Of?
A replacement car key consists of up to three parts, a blade that turns the locks, a transponder chip that the immobiliser reads, and a remote that locks and unlocks the doors at a distance.
- The blade. The blade is the metal part of the key, cut to the pattern that the locks of one car read.
- The transponder chip. The transponder chip is a coded component in the head of the key or inside the fob. The immobiliser reads it and allows the engine to start for a key that it holds in its memory.
- The remote. The remote is the part with the buttons, which locks and unlocks the doors at a distance.
A mechanical key is a blade alone and takes cutting alone. A key with a chip or a remote takes programming as well. The guide to the types of car keys shows how to tell which one a car uses.
A car key lost, broken or worn in Leicester or Leicestershire? Call Matt with the registration and the keys still held, and a quote is agreed before work begins.
Call Matt on 0116 442 2084What Are the Stages of Replacing a Car Key?
Five stages replace a car key, identifying the key type, sourcing the cuts, cutting the blade, programming the key to the car, and removing missing keys from the immobiliser memory.
- Identify the key type. The make, the model, the year and the registration identify the key that the car uses and the security system behind it.
- Source the cuts. The cuts are the pattern of the blade. They come from a working key, from the key code of the vehicle, or from a lock of the vehicle where no key is left to copy.
- Cut the blade. A machine removes metal from a blank blade until its cuts match the pattern.
- Programme the key. Programming registers the chip of the new key with the immobiliser, so that the engine starts, and pairs the buttons of a remote with the central locking of the car.
- Remove the missing keys. After a loss or a theft, missing electronic keys are removed from the immobiliser memory where the vehicle supports it. A spare key skips this stage, because no key is missing.
The order holds for each key type. A mechanical key ends at the third stage, and with no key left, entry to the car comes before the first stage.
Who Replaces a Car Key?
A car key is replaced by an auto locksmith or by a dealership of the make, and the two routes differ in where the replacement key is made.
A mobile auto locksmith makes the key where the car stands, at a home, a workplace or the roadside. A dealership makes or supplies the key through its own site. With a working key the car drives to either route. With no working key the car does not move under its own power, so the key is made at the car or the car is taken to the key.
Key work touches the security of the vehicle, so access to the information behind it is controlled. SERMI is the scheme that approves independent operators for access to security related repair and maintenance information for motor vehicles. Inta-Lock is SERMI accredited.
Capability varies by make, model and year on either route. Whether a car is among supported vehicles for a replacement key is confirmed on the call.
What Do You Have Ready Before a Key Is Replaced?
Five things are ready before a key is replaced, the registration, the details of the car, the key type with the keys still held, the place the car stands, and documents for identity and authority.
- The registration. The registration number identifies the vehicle on the call about a key.
- The make, the model and the year. The make, the model and the year identify the key that the car uses and the security system behind that key.
- The key type and the keys still held. The buttons and the blade describe the key, and the number of keys that still work sets the stage at which the replacement starts.
- The place the car stands. A mobile locksmith works at the vehicle, so the address of the car and the access to it are part of the call.
- Identity and authority documents. 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.
Say what happened to the old key as well, whether it is lost, stolen, broken or worn. That fact decides whether the removal of missing keys is part of the replacement.
What Decides the Cost and the Time of a Replacement Key?
The cost and the time of a replacement key are decided by the key type, the number of working keys left, the make and its security system, and the place and hour of the work.
Each part of the key adds work. A mechanical key takes cutting, a transponder key adds programming, and a remote key or a smart key adds electronics and pairing. Across the general market the cost and the time rise in the same order.
The number of working keys is the factor an owner controls. A spare starts with a pattern to copy. A key made after every key is lost adds entry to the car and cuts sourced with no pattern.
This guide prints no price and no duration. The cost and the time for one car are confirmed on the call, and a quote is agreed before work begins.
What Happens to the Old Key After a Replacement?
The old key is dealt with according to why it was replaced, a lost or stolen key is removed from the immobiliser memory where the vehicle supports it, and a worn or broken key in the hand of the owner raises no security question.
When keys are 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. So after a theft the electronic side and the mechanical side of the old key are two separate questions.
A used car bought with one key is the same case. For a second hand vehicle bought with only one working key, the car security guidance of Thatcham Research is to have the missing keys deleted and a spare added as soon as possible. The police guidance on vehicle theft says the same, reprogramme the keys of a second hand car.
Whether a lost key that turns up later is programmed back to the car is confirmed on the call.
Where Does Key Replacement Meet Other Key Work?
Five neighbouring questions sit at the edge of car key replacement.
How Does Replacing a Car Key Differ From Repairing One?
Replacing a car key makes a new key, while repairing a key keeps the old key and restores the part that failed, such as the case, the buttons or the blade.
The replace or repair decision, and the work of a new key cut and programmed at the vehicle, sit on the page for replacement car keys in Leicester.
What Changes When No Key Is Left to Copy?
With no key left to copy, the replacement starts with entry to the car, and the cuts come from the vehicle and not from a key. No stage is skipped.
The guide to getting a replacement car key without the original sets out what takes the place of the missing key.
Is a Key That Stops Working Always Replaced?
No, a key that stops working is not always replaced, because the cause sits in the key, in the car or in the link between the two.
The guide to a car key that is not working covers fault finding for a key that has stopped working, before a replacement key is considered.
Which Factors Set the Figure for One Car?
Six factors set the figure for one car, the key type, the working keys left, the make and its security system, the time, the place and the route. The guide to what sets the cost of a replacement car key gives the direction of each factor and prints no price.
Is a Spare Key Made the Same Way as a Replacement Key?
Yes, a spare key is made by the same stages as a replacement key, with a working key in hand from the first stage to the last. It is the opposite of the case where every key is lost, and the one situation in the table that an owner chooses in advance.
The stage a replacement key starts at for your car is confirmed on the call, and the phone is answered 24 hours a day, every day of the year.
Frequently Asked Questions
Is a car key replaced when no original key is left?
Yes, a car key is replaced with no original key left, because the cuts are sourced from the key code or from a lock of the vehicle and the new key is programmed to the car.
With the last key gone, the work starts with entry to the car.
Does a replacement car key always take programming?
No, a replacement car key takes programming only where the car has an immobiliser or the key has a remote, and a mechanical key takes cutting alone.
The key type decides it.
How long does car key replacement take?
The time car key replacement takes depends on the key type, the number of working keys left and the security system of the car, and no single duration covers every car.
The time for one car is confirmed on the call.
Does a lost key still start the car after it is replaced?
A lost key does not start the car once it is removed from the immobiliser memory, and 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.
What is checked before a replacement car key is made?
Identity and authority to request the work are checked before a replacement car 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.