What Happens When Car Key Cloning Goes Wrong

To many drivers, cloning a car key sounds like a quick, cheap fix: “Just copy the data from my working chip onto a new one job done.” But what looks simple on YouTube or forums often turns out very different in real life. In fact, a failed cloning attempt can leave you with far bigger problems and costs than simply having a proper spare made by a specialist.

Let’s look at why.

How car key cloning actually works

Every modern car key or keyless fob contains a transponder chip. This chip stores a unique code that “talks” to your car’s immobiliser; if the codes match, the car allows the engine to start.

Cloning doesn’t mean programming a new key properly it just copies that code from your original working key onto another blank chip or fob. In theory, it’s quick and cheap.

What can go wrong

In practice, quite a lot:

1. Damaging the original chip. Cheap or badly used cloning tools can corrupt or even wipe data from your working key. Suddenly, your original key stops starting the car.
2. Incomplete copy. Some cloning attempts miss important security data or synchronisation codes. The new key might open the doors but fail to start the engine.
3. Key conflict. If your car sees two keys with exactly the same ID, the system can block both, suspecting attempted theft.
4. Immobiliser sync issues. On certain cars, a failed clone can confuse the immobiliser, making it reject all keys until it’s reprogrammed by a professional.

Why “cheaper” car key often ends up costing more

It feels logical: cloning is cheaper than buying an official spare key from the dealer.

But if it goes wrong, the fix can cost far more:

• Resetting or reprogramming the immobiliser.
• Ordering and coding an entirely new set of keys.
• In worst cases, replacing parts of the car’s ECU or key module.

And worst of all the problem often shows up at the worst possible moment, like when you urgently need the car.

In this article earlier we talked in detail about why it is dangerous to buy car keys on ebay

How to do it safely

Only use trusted auto locksmiths who work with certified equipment and know the specific systems in your car.

1. Ask if they’re using a genuine blank transponder chip cheap unbranded chips are far more likely to fail.
2. Check if they back up your original key’s data first, so it can be recovered if something goes wrong.
3. Avoid “we can clone it in 5 minutes” stalls in shopping centres or car parks; most use cheap devices that don’t support modern encryption.

If your cloned car key stops working what next?

At Phoenix Car Keys, we can:

• Properly diagnose both your original and cloned key.
• Check for data corruption or missing codes.
• Recover the original key’s data or create a brand-new properly programmed spare key.
• Explain clearly what happened and how to prevent it in future.

We’ve seen plenty of cases where a quick attempt to save £20 ended with the car refusing to start entirely. Better to do it right the first time.