Key Programming & Transponders

The majority of car keys from 1995 onwards contain a security chip in the head of the key, called a transponder. This is a tiny electronic device, which communicates with the cars engine control unit, ensuring the correct key is being used.

What is a Transponder and how do they operate ?

The word transponder basically a shortened version of the words " Transmitter" and "Responder". In this case it is a minaturised electronic chip that has a nonvolatile memory; this type of memory does not need a source of energy for retention. The chip is accompanied by a fine wire coil, which acts as a transmitter.

The transponder used on vehicles today are known as "Magnetic Coupled Transponder Systems". These systems are passive in nature and therefore do not require constant electricity or thier own power supply.

The transponder chip itself does not have to be directly visable to be able to communicate. It's radio frequency can pass through materials such as rubber and plastic.

A transponder system functions around two primary components, the processor/interrogator and a transponder microchip embedded in the head of the ignition key.

The processor interacts with the vehicles engine and control unit (ECU). When an attempt to start the vehicle is made, the interrogator sends a radio frequency to an antenna.

The radio frequency contains a code number, which is usually made up of a 32 digit alphanumeric sequence. If the processor recognises the code sent by the interrogator, the vehicle will be allowed to start. If the code does not match, the vehicle may start temporarily, then shut down, or it may not start at all.

Manufacturers currently developing transponder systems are Philips, Texas Instruments, Temic and Megamos. Each have their own idiosyncrasies regarding cloning duplicate keys.

Some transponders keys can be cloned using reader/encoder hardware and writable transponder chips. Others must be programmed into the processor/interrorgator before they will function.

Other keys must be programmed using specialised diagnostic equipment.