25 May 2026 · 4 min read
A transponder key looks identical to a regular car key from the outside, but contains a small chip that communicates wirelessly with your car's immobiliser. Without the correct signal the engine will not start, even if the key fits the lock perfectly.
How does a transponder key work?
Inside the plastic head of your key sits a passive RFID chip. When you insert the key in the ignition, the car sends a radio signal to the chip. The chip replies with a unique code. If the code matches, the immobiliser unlocks the engine. If it doesn't, or if there is no code, the car will not start, regardless of how the key looks physically. This system was introduced in the mid-1990s to dramatically reduce car theft.
When does the transponder stop working?
There are a few common causes. The chip is damaged by exposure to strong magnets or physical shock. The key has lost its pairing with the car, for example after a battery replacement or ECU reset. You had a copy cut at a key-cutting kiosk, but the chip was not copied, the key fits mechanically but the car doesn't recognise it. In all these cases we can reprogram the chip at your location.
Reprogram or replace the transponder?
If the chip is still intact, we first attempt to reprogram it to your car. If the chip is damaged, we replace it with an OEM-specification chip. We use professional equipment compatible with all common passenger cars. After programming we test the key for locking, unlocking and starting, so you can be sure everything works.