Car unlocks but won't start? Buttons dead but the engine runs? Bought a key that won't work? Car key programming sorts most of these at the car, but we diagnose first, because programming doesn't fix every fault that looks like a key problem.
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Diagnosis first
Diagnosis before programming • Transponder, remote and smart keys • Around 90% of vehicles covered • 12-month key guarantee • 450+ reviews
Often it's programming, but not always. A key can lose its place in the car's memory, a remote can fall out of sync, or the fault can sit in the antenna, a module or the battery. We find out which before quoting, so you only pay for the fix your car actually needs.
Whether you've searched for car key programming near me from a car park or your driveway, we come to the car. Mobile car key programming means same-day visits for most vehicles, Monday to Friday until 10pm and weekends 10am to 6pm.
How it works
Car key programming registers a key with the car's security system, so the immobiliser lets the engine run and the remote talks to the locks. How it's done depends on where the manufacturer stores the key data.
Inside the key head sits a transponder chip that needs no battery, and it's what transponder key programming is all about. Every time you turn the key or press the button, an antenna ring around the ignition, or near the start button, reads the chip and passes its answer to the immobiliser. If the answer matches a key on the car's list, the engine is allowed to start. Programming means putting a new key on that list, or putting an old one back.
On a large share of cars, we connect to the diagnostic socket and run the manufacturer's key procedure. A handful of makes, Vauxhall, Peugeot, Citroën and certain MGs, won't accept a new key without a manufacturer security code, purchased using the car's ownership details. Renaults need the correct chip type, and on later Stellantis cars we support the battery during programming, because a voltage dip at the wrong moment can damage the electronics.
Some cars hold key data in a dedicated module. On a BMW, earlier cars store keys in the CAS module and later ones in the FEM or BDC. Mercedes-Benz uses the EIS. Peugeot and Citroën use the BSI, Volvo the CEM, and certain generations of the Audi A4 and A5 the BCM2. Older Volkswagen group cars keep the immobiliser in the instrument cluster. Where the diagnostic route isn't enough, we work with the module directly, and the original data is always saved first.
The remote buttons are often a separate step from the chip, which explains a key that starts the engine but won't lock the doors. On keyless cars, including Volkswagen group models with KESSY, the proximity side is set up too, so the car still unlocks as you walk up and starts with the button.
Pricing
Car key programming is priced from your registration and the symptom, before we travel. A key added through the diagnostic port costs less than module-level work, and programming alongside a working key costs less than starting with none. You'll know the figure before we start.
There's no upfront payment and no hidden extras. Every price is given before anything is taken apart; if one symptom could be more than one fault, you hear each possible price on the phone first, then we confirm at the vehicle. Every key we program is guaranteed for 12 months.
Symptoms
Four situations cover most programming calls, and each points somewhere different.
The remote is working, so the radio side is fine; it's the chip the car isn't accepting. A flashing key light on the dash backs that up. A dropped key, a damaged chip or a key that's dropped off the car's list are the usual causes, and reprogramming or a new chip usually sorts it.
The opposite case: the chip is fine and the remote has lost sync, or its battery has died. Try a fresh battery first. If that doesn't do it, the remote needs re-pairing, which is key fob programming rather than a whole new key.
Usually a flat fob battery, especially on cars like the Nissan Qashqai. Most keyless cars have a backup spot, often by the start button or steering column, where the fob can be held to start the car. If a new battery doesn't cure it, the fob or the car's receiver needs testing.
Online keys are a gamble: chip, frequency and blade all have to match your car, and second-hand keys are frequently tied to the car they came from. Honda keyless fobs only work with the right part number. Check with us before you buy; a photo and the registration is enough for us to say yes or no.
By make
Most makes are routine. A few have rules worth knowing before you call.
Vauxhall, Peugeot, Citroën from 2019, and some MGs: a manufacturer PIN comes first. Earlier models need no PIN. Have the V5C and photo ID ready, and the job carries on without delay.
Renault needs the exact chip type, and many use a keycard. Mazda keys from the wrong source often leave a warning light on; the keys we supply avoid that. Some Suzuki models need a specific procedure that takes a little longer. Kia: a lot of 2018-on cars only accept a genuine Kia key. BMW, Ford to 2023, Toyota, Nissan and Volvo are routine work.
Related services
Every key gone? That's car key replacement. Got one and want a backup? See spare car keys. Key won't go round at all? Look at ignition repair. Snapped blade or split case? Car key repair may be all it takes.
FAQ
Yes. Car key coding, key programming and car key programming all describe the same job: registering a key's chip, and usually its remote, with the car's security system. Some people say "coding" for the chip and "pairing" for the remote buttons, but either way the result is a key the car recognises and accepts.
On most modern cars, no. Adding a key needs diagnostic equipment, and on some makes a manufacturer PIN or module-level access as well. Some remotes can be re-synced by the owner using steps in the handbook, but the immobiliser chip almost always needs professional equipment. A failed DIY attempt can lock the system and make the job bigger.
It shouldn't, unless you want it to. When we reprogram or add a key, every key you still have is registered at the same time, and any lost key can be left off the list deliberately. Bring all your keys to the car so each one is included, and we'll test them all before we leave.
Usually. If the chip is fine and only the remote buttons have stopped working, key fob programming re-pairs the remote to the car without touching the rest of the key. If the remote's circuit board has failed, it can often be replaced inside the existing case. We test the fob first so you know which you need.
Yes. Transponder key programming covers older keys with a basic chip and no remote, right up to current smart keys. Older systems are often the quickest of all, and a worn blade can be cut fresh from the factory code while we're there, so the new key turns as smoothly as the original did.
Sometimes. On some cars, a flat battery can upset the body control module, and the symptoms look like a key fault. On the first-generation Jaguar XF and the Corsa D, the fix is dealer-level software, not a new key, and we'll tell you that rather than sell you one.
Compare
For most cars, a mobile locksmith is the quicker route, because the work comes to the car. The dealer is still the only option for a few newer models.
With every key lost, Volkswagen and Audi from about 2018, many Mercedes-Benz from about 2013, and Porsches beyond about 2015 go to the dealer. We can still add spares to many of these, and we'll tell you on the phone which applies, from your registration.
A key cut perfectly by a high-street shop opens the doors and may even turn in the ignition, but without its chip programmed, the immobiliser keeps the engine off. Mobile car key programming finishes that job at the car, and every function is tested in front of you.
From the van
November 2025Range Rover Sport
Smart key programmed on a Range Rover Sport for a customer in Portsmouth, done on site from the SmartTech mobile workshop. Programming was carried out at the vehicle, then every function was tested so the key worked exactly like the original.
Portsmouth
May 2026Peugeot 2008
Smart key programmed on a Peugeot 2008 for a customer in Winchester, done on site from the SmartTech mobile workshop. The key was coded to the car's immobiliser through the diagnostic port, with remote buttons and keyless functions checked afterwards.
Winchester
May 2025Renault Clio
Key card programmed on a Renault Clio for a customer in Portsmouth, done on site from the SmartTech mobile workshop. The key was coded to the car's immobiliser through the diagnostic port, with remote buttons and keyless functions checked afterwards.
Portsmouth
What customers say
"I cannot recommend Alec enough. My transit custom lock was not turning. I did not know Alec at this point and called another locksmith. To cut a long story short the other locksmith attempted a repair and then gave up, leaving me with a van I could no longer use. I called Alec who came out next day; he repaired the damage done by the other locksmith and custom made a replacement ignition barrel so one key still does the doors and the new ignition. I couldn't be more pleased. Price was very fair too!"
"Did the work at a 3rd of the price of the dealership and I'm sure to a higher quality, the work was quick and professional. Could not recommend more!"
"Absolutely spot on! After ringing about 15 different companies who said they couldn't help and one company even saying the series of my car doesn't exist I found smarttech who I contacted who could finally help! The next day he came out and I now have access and a new key to my car! Fast and efficient polite service! Highly recommend!!"
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