The key light
is flashing

A flashing key symbol means the car has looked for its key’s chip and not found one it trusts. That tells you where the conversation broke down, not which side broke it.

Try these first

1. Use the spare key, if you have one. If it starts, the fault is in the first key.
2. Hold the key against the start button or barrel; some cars read a weak chip better up close.
3. Check whether a battery was changed or went flat recently.

Why it is often the reader

The chip is read by a small coil around the ignition barrel. When that coil fails, a perfectly good key is ignored. It is a common fault and a cheap part.

When the coding is lost

Some cars lose their list of trusted keys when the battery goes flat or is disconnected. The keys are fine; the car has simply forgotten them. That is reprogramming rather than new parts.

What we do

We read the fault codes, test the key and the reader separately, and tell you which it is. If it turns out not to be the immobiliser, we say so. The immobiliser page has the prices.