What is a Transponder Key? How Does It Work?

Written by

Charles Bolte


Vernon Hoppe 

what is a transponder key

Car security is a big concern to most car owners. And a significant contributor to security is the car keys that ensure your car is safely locked when you are not using it.

For the past 2 decades, most modern vehicles have come equipped with transponder keys for enhanced security. But what is a transponder key? This key has a built-in electronic microchip that sends a coded message to the car.

In fact, when you insert the transponder key in a chip key car ignition, a unique coded signal is transmitted into the car to unlock the engine.

Brief History of a Transponder Key

To get a better transponder key meaning, remember the name transponder is coined from a combination of 2 names: transmitter and responder.

Interestingly, the idea behind today’s vehicle transponder started way back during the World War 2 era. Military planes used coded messaging that made them easily identifiable on the radar to differentiate them from enemy planes.

To date, the aviation industry still embraces this technology to enable air traffic controllers to identify and locate planes flying within their airspace.

But, it wasn’t until the mid-80s when car theft was rampant, that chip code messaging was utilized for a car. In 1985, General Motors created a transponder chip key for its Corvette model.

This caused a sharp decline in theft cases, and by the late 90s, most car models were embracing this technology.

Features of Different Transponder Systems


Transponder key features vary from model to model. Here are the most common types:

1. Keyless Entry Remote

This feature was first brought to the market by Ford in 2006 and included a remote with 3 or 4 buttons and a standard eight cut key blade.

They are designed to ensure it’s hard for one to gain entry into the car without the keyless remote. The key only opens the door when the remote is within a certain range of the car.

2. Flip Remote Keys

The flip remote key is mostly found in General Motors vehicles. The metal key is inside the fob and flips out when in use. When not using it, it folds back into the fob.

3. Passive Anti-Theft System (PATS)

This transponder key has a PATS programmed to the car’s ECM (Engine Control Module) and was introduced by Ford in 1996.

If you lose the key and need a replacement, the old code in the car has to be cleared and a new one reprogrammed into a new key, which makes the old key useless.

4. Proximity System Smart Key

With this system, when you want to start the engine, you must insert the key fob into the vehicle and then push a start button on the dashboard.

The only downfall is the key has to be inserted into the vehicle to start and run the engine. There’s no other key for ignition, so losing the key fob can be inconvenient.

How Does It Work?


It is easy to know what a transponder key looks like because of its broad plastic head where the microchip is inbuilt. The transponder system is made of these components:

  1. The electronic chip key
  2. The antenna ring: induction coil around the ignition switch that detects if the key is programmed for the vehicle engine.
  3. The car’s Engine Control Module (ECM): The car’s computer
  4. The immobilizer: An Electronic security device that ensures the engine only starts when the correct key is inserted.

When you insert a transponder key into the ignition, the antenna ring sends a radio frequency code into the key’s chip. The chip then sends back its unique code through the antenna ring to the car’s ECM for authentication.

If the car identifies the code, the immobilizer disengages and unlocks the engine, allowing the vehicle to start.

Different Types of Transponder Keys


In a nutshell, there are 2 types of car key transponder chip

  1. Zero-bitted – Are usually cloned and don’t have a preset inscription code
  2. Encrypted – Contain random encryption to be programmed into a car

You can tell the difference by observing what a transponder key locksmith does when you need an extra key.

If they duplicate the key by inserting it into a tool and then doing the same with a transponder key blank, then that’s cloning, done to a zero bitted transponder key.

But for encrypted ones, the locksmith has to program transponder keys to the car’s OBD port using a special programming tool. Nonetheless, some car models are made so you can’t duplicate an encrypted transponder key without a working one.

Vehicles That Use Transponder Keys

Today, most cars have a transponder key due to its enhanced security. Here is a list of cars with transponder keys:

  1. Acura
  2. Audi
  3. Alfa Romeo
  4. BMW
  5. Buick
  6. Cadillac
  7. Citroen
  8. Chevrolet
  9. Chrysler
  10. Dacia
  11. Daf
  12. Daewoo
  13. Daihatsu
  14. Dodge
  15. Fiat
  16. Ford
  17. GMC
  18. Honda
  19. Hammer
  20. Hyundai
  21. Iveco
  22. Isuzu
  23. Jaguar
  24. Jeep
  25. Kawasaki
  26. KIA
  27. Lancia
  28. Land Rover
  29. Lexus
  30. Lincoln
  31. Mazda
  32. Mercedes
  33. Mitsubishi
  34. Nissan
  35. Opel
  36. Peugeot
  37. Porsche
  38. Renault
  39. Rover
  40. Seat
  41. Skoda
  42. Subaru
  43. Suzuki
  44. Toyota
  45. Volkswagen
  46. Volvo
  47. Yamaha

Pros and Cons of Transponder Keys

Here are a few reasons why many car manufacturers are using the transponder key


  1. Enhanced security.
  2. Easy to use.
  3. They are convenient to carry because all you need is the key fob, which is small and light.
  4. The transponder key smart features ensure you can’t leave the car keys locked inside. Additionally, if you leave with the key and forget to lock the doors, they automatically lock themselves.


As with many good things, the transponder key system has its downside. Here are some of them

  1. Costly to replace and duplicate.
  2. It is a delicate system, and so it’s prone to damage.
  3. The fact that it’s easy to operate means you will need to be more careful leaving the transponder keys around children. They might think it’s a toy and start playing with the buttons, which might interfere with the car system or become a hazard.
  4. Some keys use batteries which might become an inconvenience when they wear out when you are unprepared.

Cost to Change or Program a Transponder Key


Unlike non-transponder keys that most locksmiths can cut, the chip keys must be programmed to work with your car.

This means that unless your local locksmith has the special programming tools, then for duplication and replacement, you’ll have to visit the dealer, which is quite costly.

The price ranges between $50 to $175 for most of the vehicle models, all the way up to $1000 or more for the high-end models.

1. Compare a transponder key with other keys

Regular keys have no layer of security apart from their contours, but a transponder key and remote keys have extra layers of security.

A remote key has two layers of security; you can unlock a car by inserting the key in the car door and by pressing the buttons in the key fob from a distance.

The difference between a transponder key vs key fob is that a transponder key has a third layer of security in the microchip for sending a unique code to unlock the engine.

2. Can a transponder key prevent theft?

A transponder key prevents car theft because it reduces the chances of opening the car without its keys or ‘hot wiring’ it. They ensure the car won’t start unless it detects the serial number programmed to the key.

Frequently Asked Questions

How do I know if my car key is a transponder key?

To know that your car key is a transponder key, wrap the plastic part in tin foil and attempt to start the car. If it does not, then it’s a transponder key.

Another clue is in the price. Tell your dealer the VIN and enquire about the cost of replacing it. A transponder key will be costlier than ordinary keys.

Can I program a transponder key myself?

If you have two operational keys, you can program a transponder key. You’ll also need programming tools to understand your vehicle’s programming process.

However, if you don’t, you are better off consulting a professional locksmith for guidance.

Signs of a bad transponder key

When you start having car problems such as locking issues, the engine not starting normally, the emergency signal going off, or having problems turning it off after it’s activated, then these are signs of a bad transponder key.

Can I start my car without a chip key?

A chip key is designed to make it impossible for a transponder key bypass, which means you won’t be able to start the car if you don’t have the key. However, an authorized dealer can make another key fob for you.


Since its invention, the transponder key has revolutionized car security. This detailed guide gives you answers to various questions, including what is a transponder key? what does a transponder key do? and offer information about its features.

Hopefully, you can now embrace the new technology that makes your car more secure against thieves.

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