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How do Transponder Keys Work

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Chip Key Defined

A chip key or technically called a transponder key, gets it’s name after the electronic “chip” that is embedded into the key’s head. These keys are used by cars produced  in the last 15 years. The devices help to reduce auto thefts.

Immobilizing technology uses RFID (Remote Frequency Identification). Modern transponder keys use RFID tags to send a digital signature into the vehicle. These signals show that the driver is using a recognized to start it.

The Introduction of Immobilizing Systems

Originally introduced by General Motors to protect the Corvette, security keys protect the car from theft. Since their introduction, immobilizing systems have drastically reduced car and truck thefts by as much as 75%. The immobilizer systems typically use a computer based module and some form of chip key. When the key is turned, a digital signature is sent to the immobilizer. If the signature matches what is recorded into the immobilizing system, the car will start.

The Immobilizer System

The vehicle immobilizer system consists of: a transponder, an immobilizer, a immobilizer indicator (light) and an antenna pickup or immobilizer ring. The immobilizer and the immobilizer ring are sometimes integrated into the same part. The following explains the purpose each component of the immobilizer system:

  • Transponder – A small device often called a chip can either be made of plastic, glass or carbon. This device uses a digital memory and circuitry including a tiny coil of copper wire. The circuits allow the chip to communicate via the immobilizer ring (coil) to the vehicle’s immobilizer. Transponders can be found in either mechanical keys or proximity keys.
  • Immobilizer – The immobilizer is the device that reads the digital signature of the vehicle key and if it is correct, tells the Engine Control Module (ECU), that it is permitted to start the vehicle.
  • Immobilizer Ring – An Immobilizer Ring is found either around the mechanical ignition, the push to start button or behind a program pocket for proximity fob equipped vehicles.
  • Immobilizer Light – This indicator can be found either in the vehicle instrument cluster, on the face of the dash or the top of the dash. The light will extinguish when a recognized key is present in the vehicle.

The Immobilizer System Operation

If a driver uses a key or fob in a vehicle that they wish to drive, a different process will occur depending upon the ignition design. Here is a brief description of the two systems and their differences.

Mechanical Transponder Key Ignitions

In a mechanical transponder ignition system, the operator inserts a metal key containing a transponder chip in its head. When the key is turned, an electronic voltage is applied to the immobilizer coil that is housed in the immobilizer ring. That coil then becomes an electromagnet. 

When a transponder chip is placed inside of the immobilizer ring coil, a voltage is produced. The voltage then powers up the chip key circuitry to send its digital signal to immobilizer coil. The signal is then transmitted to the immobilizer. If the signal signature matches the immobilizer list of permitted keys, the immobilizer allows the car to start. Once the car is started, the immobilizer light goes out.

Push to Start Ignitions

Also called Passive Keyless Entry (PKE) systems or Push to Start, work in a similar way as the mechanical transponder key system. The main difference is the digital signature is transmitted using radio waves. The vehicle is designed to constantly monitor for the electronic signal transmitted by a fob. If the digital signature matches the list of permitted keys, the vehicle starts.

The basic techniques of the PKE system leave them open to attack and ultimately to vehicle theft.


Local Locksmith can program or replace lost chip and transponder keys at prices well below what the dealer charges. If you need a chip key copy, chip key replacement or chip key repair give us a call.

Call Local Locksmith TODAY!

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