Car Key Programming | Mobile Key & Immobiliser Programming
New key won't start the car, remote buttons stopped working, or the car suddenly doesn't recognise your key? We program transponder keys, remote fobs and smart keys at your vehicle, using dealer-level equipment and manufacturer-specific procedures.
- 6 years' experience
- Dealer-level diagnostic and programming equipment
- Module and EEPROM capability
- Fully mobile service
- Cars, vans, imports and smart keys
- AVG Same Day Service
- DBS Checked
- 5★ Reviews
Not A National Company
A local business, not a call centre.
Real Local Professionals
Locals, not technicians sent by a middle-man company.
No Inflated Pricing
National companies often mark prices up 2–3x. We don't.
Deal Direct With The Technician
No wondering who or when. It's always us.
Car Key Programming For Modern Vehicle Security Systems
Car key programming is the process of authorising a key with your vehicle's security system, so the immobiliser recognises it and allows the engine to start. It also covers pairing remote locking and keyless functions.
Almost every car built since the late 1990s needs it.
What Does It Mean To Program A Car Key?
Programming a car key means registering its transponder chip, and often its remote and keyless functions, with the vehicle's electronics so the car accepts it as an authorised key.
Why Won't A Replacement Key Work Until It's Programmed?
A correctly cut key will turn the locks, but the immobiliser won't allow the engine to run until it recognises the key's transponder chip.
Until that chip is programmed to the vehicle, the key is just a piece of metal as far as the engine is concerned.
Key not working? Call 023 8218 2738 or text us your registration and symptoms.
How Does Car Key Programming Actually Work?
When you start the car, the key's transponder is read by an antenna near the ignition or start button. The immobiliser checks it against its list of authorised keys, and if it matches, tells the engine ECU that starting is allowed. Programming means adding the key to that chain of trust.
The chain looks like this: key → transponder → antenna → immobiliser → security module → engine start authorisation. Where the immobiliser function lives varies by manufacturer, and that determines how we program it.
Reading The Vehicle's Immobiliser & Security System
The first step is identifying the vehicle's security system and where it stores key data, which tells us which programming method applies.
On many older Volkswagen group vehicles, the immobiliser sits in the instrument cluster, while some Audi models hold key data in a module known as BCM2. BMW uses the CAS module on earlier models and the FEM or BDC on later ones. Mercedes-Benz authorises keys through the EIS (also called the EZS). Volvo stores key data in the CEM, Peugeot and Citroën in the BSI, and Ford in modules such as the BCM or GEM depending on the model.
Programming A Key Through The Diagnostic OBD Port
On many vehicles, new keys are added through the OBD diagnostic port using programming equipment that runs the manufacturer's key learning procedure.
Some makes require a security PIN code, which our equipment can often retrieve from the vehicle. Others, including many Ford, Vauxhall, Nissan and Peugeot models, follow this route. For keyless systems, such as KESSY on Volkswagen group vehicles, the proximity function is adapted as part of the procedure.
When Module, Bench Or EEPROM Programming May Be Required
Some vehicles don't allow keys to be added through the diagnostic port alone, particularly when all keys are lost. In those cases we work with the security module directly.
This can mean reading security data from the module to prepare a key, as with many BMW and Mercedes-Benz systems, where the new key is written with vehicle-specific data rather than “learned”. Occasionally the module needs to be removed and its EEPROM memory chip read on the bench. We always back up the original data before making any changes. Most vehicles don't need this level of work, but having the capability means we can handle the ones that do.
Testing The Transponder, Remote & Keyless Functions
After programming, we test that the key starts the engine, the remote locks and unlocks, and any keyless entry and push-button start functions work correctly.
Why Is My Car Not Recognising The Key?
A car may not recognise its key because the transponder isn't authorised, the remote has lost synchronisation, the key battery is flat, the antenna or reader has failed, or there's a separate module, ignition or electrical fault.
Diagnosis comes before programming, because programming won't fix every non-start problem.
The Transponder Is Not Authorised By The Immobiliser
If the immobiliser warning light flashes and the engine cranks but won't run, or won't crank at all, the car may not be recognising the transponder.
A dropped key can damage the chip, and some keys lose their programming after electrical work. Reprogramming or replacing the transponder usually resolves it.
The Remote Works But The Car Won't Start
If the buttons lock and unlock but the engine won't start, the transponder or immobiliser side is the likely cause, not the remote.
On keyless cars, a flat fob battery can stop the car detecting the key. Holding the fob against the start button or steering column often starts it anyway.
The Engine Starts But The Remote Buttons Don't Work
If the key starts the car but won't lock or unlock it, the fob battery or remote synchronisation is usually at fault, rather than the immobiliser.
When The Fault Isn't Actually The Car Key
Sometimes the key is fine and the fault lies elsewhere, such as a failed antenna ring, a faulty module, a worn ignition barrel, a weak vehicle battery or a starter fault.
We'll tell you honestly what we find. If the problem is with the ignition, see Ignition Repair & Replacement. If a key fault has left you stranded, our Emergency Auto Locksmith service can help.
Remote, Transponder & Smart Key Programming
A modern car key is usually three things in one: a mechanical blade, a transponder chip for the immobiliser, and a remote transmitter for locking. Each can be a separate element, and each may need its own programming step.
Transponder Keys That Start The Vehicle. The transponder is a small chip inside the key head that communicates with the car when you turn the key or press start. It needs no battery, and it's what the immobiliser checks before authorising the engine.
Remote Key Fobs For Locking & Unlocking. The remote transmitter locks and unlocks the car by radio signal and is often programmed or synchronised separately from the transponder. That's why a key can start the engine while its buttons do nothing, or the other way around.
Smart Keys, Proximity Keys & Keyless Start Systems. Smart keys combine the transponder and remote with proximity functions, letting the car detect the key nearby for keyless entry and push-button start.
Additional & Replacement Keys For Cars And Vans. We program additional keys, replacement keys and reprogram existing keys for cars and vans. If you want another key while yours works, see Spare Car Keys. If no working key remains, see Lost Car Keys.
Car Key Programming By Manufacturer
BMW, Audi, Mercedes-Benz, Land Rover, Jaguar, Volvo, Ford, Volkswagen, Vauxhall, Peugeot, Citroën, Renault, Toyota, Nissan, Honda, Mazda, Hyundai, Kia, Subaru, Mitsubishi and Suzuki.
Manufacturer-Specific Immobiliser & Key Systems
Every manufacturer designs its own immobiliser architecture, which is why programming a Ford is a different job from programming a BMW or a Mercedes-Benz.
Programming Equipment For Modern Cars, Vans & Imports. We use professional diagnostic and key programming tools, along with bench equipment for module-level work, covering most European, Japanese and Korean vehicles, including many Toyota and Nissan imports.
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Send your details and we'll call you back with a price. For anything urgent, just call.
- Price explained before any work
- No upfront payment
- Deal direct with the technician
Key Cutting vs Car Key Programming — What's The Difference?
Key cutting creates the physical blade that turns the locks. Key programming authorises the key electronically so the car will start and the remote will work. Most modern keys need both.
| Function | Key Cutting | Key Programming |
|---|---|---|
| Creates physical blade or profile | Yes | No |
| Operates mechanical lock | Usually | No |
| Authorises engine start | No | Yes, where transponder-based |
| Pairs transponder | No | Yes |
| Remote functions | No | May need a separate or same procedure |
| Smart/keyless operation | No | Programming required |
Why A Correctly Cut Key May Still Not Start The Engine
A key cut perfectly to your locks will open the door and turn the ignition, but without a programmed transponder, the immobiliser will still block the engine.
Mechanical Key, Transponder & Remote Functions Explained
The blade handles the locks, the transponder handles engine authorisation and the remote handles locking by radio. We cut, program and test all three so the key works completely.
What Does It Cost To Program A Key?
There isn't one standard price for car key programming, because the procedure depends on your vehicle, the key type, the security system generation and whether you still have a working key. Adding a key through the diagnostic port costs less than module-level work. We confirm the price before starting.
Why Some Vehicles Are More Complex To Program Than Others
Vehicles with newer encryption, keyless systems or module-based key data take more time and specialist equipment than those that allow straightforward diagnostic programming.
Spare-Key Programming vs All-Keys-Lost Programming
With a working key present, many vehicles allow a simpler procedure. With no keys, the security system often has to be accessed more deeply, which adds time and cost.
Clear Pricing Before Programming Begins
You'll know the price before we begin, with no upfront payment, no hidden charges and no obligation to proceed.
If diagnosis shows the job needs different work from what was expected, we'll explain the revised price first. If you decline the revised work, there's no call-out fee.
Get a programming quote — call 023 8218 2738 or text your registration.
Keys Coded To Local Vehicles
Typical programming jobs and how they're resolved at the vehicle.
BMW Replacement Key Programmed To The Vehicle
A BMW key prepared using data read from the FEM module and programmed as a new authorised key.
Ford Remote Key Cut, Programmed & Tested On Site
A Ford remote key cut, added through the OBD port with the vehicle's PIN code, and its remote synchronised.
Volkswagen Key Recognition Problem Diagnosed & Resolved
A Volkswagen whose key stopped starting the engine, diagnosed as a transponder recognition fault and resolved through reprogramming.
See more Recent Jobs or call 023 8218 2738.
Every Key Cut, Programmed & Tested Before We Leave
We don't finish a job on the promise that a key should work. The blade is checked in the locks, the transponder is confirmed against the immobiliser, and the remote and keyless functions are tested with you present.
Programming Questions Answered
Where Programming Fits With Other Key Work
Need A New Key Because The Original Has Been Lost?
All keys lost replacement at your vehicle.
Want Another Programmed Key While Yours Still Works?
A planned second key, cut and programmed at a time that suits you.
Is Your Existing Key Physically Damaged?
Repairs, recasing and replacement blades for damaged keys.
Could The Problem Be With The Ignition?
If the key won't turn or the barrel feels worn. For all other key needs, visit our replacement hub.
Need A Car Key Programmed To Your Vehicle?
Tell us about your vehicle and the problem, and we'll give you a clear price and arrival time.
These details help us tell a straightforward programming job from a fault that needs diagnosing:
- Vehicle make, model and year
- Registration number
- Number of working keys and type of key
- Whether the engine starts
- Whether the remote buttons work
- Any immobiliser or key warning on the dashboard
- Where the vehicle is
We cover Eastleigh, Chandler's Ford, Hedge End and the surrounding areas, or contact us online.