Houston Local Locksmith

TXDPS - B20292


Transponder Car Keys

About The Transponder Car Keys.

Function-Added Security.

When the correct mechanically cut key is turned in the ignition, the engine control unit (ECU) on the car sends an electronic “coded message” to the key, and it will only allow the car to start if “coded message” on the key matches. This additional security is intended to reduce the risk of auto-theft.

How Does A Transponder Car Keys Work?

In basic terms a transponder is a miniaturized electronic chip that has what is called non-volatile memory. Non-volatile memory is the type of memory that does not need constant energy for retention. Along with that electronic chip is a set of windings; very fine wire coiled around a tube. These windings look similar to the windings you would find in an electric motor.

Automobile manufacturers utilize magnetic coupled transponder systems. Magnetic coupled transponder systems are passive in nature. This means they do not require constant electricity and do not need a power source of their own. They operate in the frequency range area of 125 kHz. Since magnetic coupled transponders do not have their own power source they are very limited in range of communication and generally operate in the range of ½” to 6”. Since this is a radio frequency it can penetrate materials that would make the transponder not directly visible, such as the plastic or rubber in the bow of a key or fob.

The process of key identification is similar in most automotive transponder systems. Once a key is inserted into the ignition lock and turned to one of the ‘on’ or ‘run’ positions, the induction coil that is mounted around the ignition lock sends out an electromagnet field of energy. The windings in the transponder chip absorb that energy and power the electronic chip to emit a signal.

The signal is usually a unique alpha-numeric sequence which is considered the identification code. The induction coil reads the signal and sends it to some type of computer device to recognize the signal. If the signal is recognized as being already in the computer’s memory the signal is accepted and other electronic components in the vehicle are set into motion to allow the starting of the vehicle or the continuation of the engine running.

Programming Requires Specialized Equipment & Training.

Remote keyless entry fobs emit a radio frequency with a designated, distinct digital identity code. Inasmuch as “programming” fobs is a proprietary technical process, it is typically performed by the automobile manufacturer but trained and qualified technicians may be found at many locksmith, hardware and even battery supply businesses (In point of fact it is a computer in the car which is programmed in the process, not the fob itself.) In general, the procedure is to put the car computer in ‘programming mode’. This usually entails engaging the power in the car several times while holding a button or lever.

It may also include opening doors, or removing fuses. The procedure varies among the various makes, models, and year of the vehicle. Then, once in ‘programming mode’ one or more of the fob buttons is depressed to send the digital identity code to the car’s onboard computer. The computer saves the code and the car is then taken out of ‘programming mode’ and the vehicle is ready to go.


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