Automotive key programming explained
What key programming actually does, the difference between cloning and programming, what all keys lost needs, and how to tell which route a job takes.
Cutting a key and programming a key are two different jobs, and most of the confusion in this trade comes from treating them as one. This page covers the programming half: what it is, when a key can be cloned instead, and what to establish before you quote.
What programming actually does
A modern car will not start unless the immobiliser recognises the transponder in the key. Programming is the process of writing a new key's identity into that immobiliser, or writing the immobiliser's expected identity into the key. Which direction you work in decides the tools you need.
A cut key with no programming turns the ignition and does nothing. A programmed key that has not been cut starts nothing, because it will not turn. Both halves have to happen, and they can happen in either order.
Cloning versus programming
Cloning copies an existing working key onto a blank. The car is never involved, which makes it fast and makes it possible without any connection to the vehicle. It only works on fixed code transponders, and it only works if you have a key that already starts the car.
Programming writes to the immobiliser itself. It is the only route when every key is lost, when the chip uses a rolling code, or when the vehicle keeps a count of how many keys are authorised.
- Fixed code, cloneable: the 4C and 4D families, and ID46 in many cases.
- Rolling code, must be programmed: ID47, ID49 and 8A.
If the chip is not printed on the key, a transponder reader identifies it in seconds. Every product page here states the chip where we hold it confirmed, and leaves it blank where we do not.
OBD, bench, and why it matters to your quote
Some immobilisers accept a new key through the OBD port with the car sitting there, in minutes. Others need the module read on the bench, which means removing it from the vehicle, which changes the job from a roadside call into a workshop visit. A third group needs a PIN or security code read separately before anything can be written at all.
This is the single biggest variable in what a job costs you, and it is decided by the vehicle, not by the tool. Establish it before you quote, not after.
All keys lost
All keys lost is often possible and occasionally is not, and again it depends on the platform rather than the programmer. Where it is possible it usually takes longer than adding a spare, because the tool has to establish authorisation from nothing rather than from a working key.
Every tool listed here states which procedures its manufacturer supports on its own page. We will not tell you a platform covers your vehicle unless the manufacturer says so.
What to establish before you quote
- Does the customer have a working key, or is this all keys lost?
- What transponder family is in the existing key, if there is one?
- Is the procedure OBD or bench on this platform?
- Is a PIN or security code needed first, and can you read it?
- Do you need to cut a blade as well, and do you have the keyway?
Questions
Do I need a separate tool for cloning and for programming?
Not necessarily. Several platforms do both, and the product page for each states which functions it covers. A dedicated cloning device is cheaper and faster if cloning is most of your work.
Will a programmer work on every make?
No tool covers everything, and any that claims to should be treated with suspicion. Coverage is published by each manufacturer per platform and per procedure, and that is the list to check.
Does a software subscription come with the tool?
It depends on the tool. Where a licence or update subscription is separate, it is stated on the product page rather than implied.
About this guide
This is general information about how the work is normally done, not advice for the particular vehicle, lock or machine in front of you. It does not replace manufacturer instructions, training, or your own judgement about whether a job is within your competence. Specifications and fitment change between model years, so check the code on the original part before you buy or cut anything. See the terms.