What programming actually does
Inside every modern car key is a transponder chip carrying a unique code. Turn the key or press the start button and the car sends out a challenge. If the chip answers correctly, the immobiliser releases and the engine is allowed to run. If it does not, you get a few seconds of cranking and nothing else.
Programming is the process of teaching your car to accept a particular chip. It is done through the vehicle's diagnostic port with equipment that can talk to the immobiliser and, on many cars, to the body control module that handles the remote buttons.
The three things that get programmed
| Part | What it controls |
|---|---|
| Transponder chip | Whether the engine is allowed to start |
| Remote buttons | Central locking, boot release, alarm arming |
| Proximity or smart key | Keyless entry and push button start, key stays in your pocket |
A key can have one of these working and not the others, which is why a car that unlocks on the fob but refuses to start is such a common call. The remote is paired, the chip is not.
Jobs that need programming
- A new or spare key that has just been cut
- A second hand or online key that came from another vehicle and is still coded to it
- A key that has stopped being recognised after a flat battery or a jump start
- A replacement ignition barrel or immobiliser component
- An all keys lost situation, where the car has to accept a completely new key
- Deleting keys you no longer have, covered on our lost or stolen key deletion page
Buying a key online first
Plenty of people do, and sometimes it works out well. Sometimes it does not, and it is worth knowing why before you spend the money.
Keys come in different frequencies and different chip families, so a key that looks identical to yours can be the wrong part entirely. Some second hand keys are locked to the car they came from and cannot be recoded. Some cheap fobs have poor quality boards that fail within months.
Send us a photo of your existing key and the make, model and year before you buy, and we will tell you what to look for. We would rather do that than turn up and charge you for a journey to tell you the key is useless.
How long it takes
With a working key already in your hand, programming a spare is usually a matter of minutes once we are connected to the car. An all keys lost job takes longer because the security system has to be persuaded to accept a new key with no existing one to authorise it.
A handful of manufacturers build in a security delay that nobody can shorten, where the car waits before it will accept the change. We check that against your model on the phone so you know what to expect before we arrive.
When programming will not fix it
Being honest about this saves everybody time. If the immobiliser itself has failed, if there is damage to the transponder ring around the ignition, or if a previous attempt has left the module in a bad state, programming a key will not fix the car. That is a diagnostics job and possibly immobiliser work.
We would rather find that out with a diagnostic scan in the first ten minutes than sell you a key that was never going to solve the problem.
Mobile across Leeds
All of this happens at the car. Driveways in Horsforth, work car parks around Seacroft, student streets in Headingley, and every postcode in between, 24 hours a day.
Programming at the roadside
All of this happens through the car's diagnostic port, which means the only thing we need is access to the vehicle. We program keys on driveways in Horsforth, in hospital car parks around Seacroft and on the permit streets of Headingley where moving the car is not an option.
One practical note. Programming draws power, and a car with a tired battery can drop out halfway through a session, which is worth avoiding. If your battery has been struggling, mention it when you call so we can plan for it rather than discovering it at the worst moment.
Questions about car key programming
Can you program a key I bought online?
Usually, if it is the right frequency and chip type and not locked to another vehicle. Send us a photo and your vehicle details before you buy and we will check.
My fob locks the car but it will not start. Why?
The remote side is paired but the transponder is not being recognised. That is a programming job, and it is one of the most common calls we get.
How many keys can be programmed to one car?
It varies by manufacturer, commonly between four and eight. We will tell you the limit for your vehicle.
Will programming a new key wipe my existing ones?
Not normally. On some models the procedure does reset all keys, in which case bring every key you own to the visit. We will warn you beforehand.
Do you need the car's registration?
Yes, plus make, model and year, and ID with proof you keep the vehicle.
Can you program keyless smart keys?
Yes, for most makes and models. A few very recent vehicles need manufacturer online access and we will tell you if yours is one.
How long does it take?
Minutes for a spare when you have a working key, longer for all keys lost, and some models have a manufacturer security wait built in.