Car Transponder Chip

Features

1, Compact Size

Designed to be small and easily embedded into space-constrained housings.

2, Enhanced Reading Performance

Each car transponder chip is optimized for reliable, stable reading and writing performance.

3, Excellent Consistency

Specifically designed for car key applications, ensuring flawless operation without compromising functionality.

Immobilizer

Since 2000, nearly all vehicles come equipped with an immobilizer system. To start the engine, the driver must use a car key embedded with an RFID transponder, which is much harder to duplicate than a traditional mechanical key. This system has greatly reduced car theft and is now a standard feature in modern vehicles.

Both the ECU (Engine Control Unit) and the RFID transponder in the immobilizer system share a secret value. They exchange this confidential data through a secure process known as encrypted mutual authentication.

When monitored, the communication between these two devices appears as a random signal, making it nearly impossible to interpret. By verifying both the mechanical key blade and the RFID transponder, the system ensures that the engine cannot be started without the correct car key.

What a car transponder chip is

A car transponder chip is a small passive RFID device built into the head of a vehicle key or key fob. It has no battery: when the ignition antenna energises it, it answers the immobiliser with a stored code, and the engine control unit only allows a start if that code is valid. Since about 2000, nearly all cars have shipped with such an immobiliser, which is why a modern key is far harder to copy than a plain cut blade. The chips run in the low-frequency band, 125 kHz for the HITAG and Megamos families and 134.2 kHz for the Texas Instruments types, and come as a small glass tube, a carbon or ceramic slug, or a moulded (EMC) package that drops into the key housing.

Which chip is which

Immobiliser chips are usually referred to in the trade by 'ID' numbers as well as their real part names. The label tells a locksmith which technology, and which programming tool, a key needs. The table below maps the common labels to the underlying chips; always confirm the exact chip against the actual vehicle or a working key, not the ID label alone.

HITAG 2 is an NXP part. On our verified HITAG 2 card page its crypto mode is the one used in vehicle immobilisers, and it works at 125 kHz. Megamos, the VAG-group chip commonly labelled ID48, is an EM Microelectronic part. The Texas Instruments 4C and 4D types work at 134.2 kHz. The T5577 is a programmable 125 kHz transponder (Microchip ATA5577C) that can be written to present open, fixed-code formats, which is why it is used to clone read-only keys; it cannot reproduce a rolling crypto key.

Cloning versus programming: what a key actually needs

Two different jobs are both loosely called 'copying a key', and the chip decides which is possible.

• Fixed-code chips (older read-only types, and a T5577 blank encoded to match) can be cloned: a programmer reads the original's code and writes it to the new chip, and the immobiliser cannot tell them apart.
• Crypto chips (HITAG 2 / ID46, Megamos / ID48, TI DST / 4D) use a secret key and a challenge-response exchange, so they cannot be cloned by reading. A new key has to be programmed to the car: the transponder is written with the right data and the immobiliser is taught to accept it, usually through the OBD port with dealer or aftermarket key-programming equipment and, on many cars, a PIN or security code tied to the vehicle.

Either way the work needs a transponder programmer or key-programming tool that supports the specific chip and vehicle. We supply the chips; we do not program keys to vehicles or defeat immobiliser security.

Glass, carbon and EMC formats

The same chip is offered in more than one body. A glass-tube transponder is the classic cylindrical bead that sits in the key head; a carbon or ceramic slug is a robust alternative; and an EMC (moulded) package is shaped to drop into a particular key housing. The transponders we supply are rated IP68 and can be laser-marked with a logo or number. Tell us the housing you are fitting and we match the format.

A note on immobiliser transponders versus gate and parking systems

The transponder in a key is a low-frequency immobiliser device that works over a few centimetres at the ignition. It is a different thing from the vehicle RFID used at car-park barriers, gates and yards, which is a UHF windshield tag read from several metres. If your project is reading vehicles as they approach a gate rather than authorising an engine start, see our vehicle RFID identification guide instead.

Before you order

1. The exact chip or ID type your vehicle uses, or a working key or your reader details so it can be confirmed; do not rely on the ID label alone.
2. The format: glass tube, carbon/ceramic slug or EMC moulded package, and the housing it must fit.
3. Fixed or rewritable, and whether you need a blank (for example a T5577) or a specific crypto part.
4. Any laser marking (logo or number).
5. Quantity and delivery date; note that we supply the chips and do not program keys to vehicles.

What Proud Tek supplies

We supply car transponder chips in glass, carbon and EMC formats on HITAG, Megamos, Texas Instruments and T5577-class parts, quote-only, with laser marking on request. Proud Tek has manufactured RFID products in Shenzhen since 2008; standard samples are free and standard lead time is 2 to 3 weeks. We do not program keys to vehicles, defeat immobiliser security, or advise on bypassing it. Start on the contact form, by email or on WhatsApp; see the HITAG 2 card for the 125 kHz crypto part, or browse all RFID tags.