A transponder chip deactivates a motor vehicle immobiliser when the car key is used to start the engine. The majority of keys to vehicles built just after 1995 include transponder chips.  When the vehicle key is turned in the ignition, the engine control unit (ECU) on the vehicle sends an electronic message to the key, and it will let the car to start only provided it receives the accurate message back. So even for a simple car key without any buttons, the key must be cut properly to switch the locks and also programmed appropriately to deactivate the immobiliser. Car keys with chips can be programmed by special programmers using by a professional locksmith.
The Reason That Automotive Manufacturers Use Transponder Keys?
They are used to prevent the vehicle from being hot wired. The car will not even start if the device at the switch does not detect the low level indicator through the key. If a copied key is used without the proper signal, the vehicle will not start. When someone tries to hot wire the vehicle, the vehicle will not start because there is no sign coming from the key.
How Can you Tell If your vehicle Come With A Transponder Key?
In most situations, the plastic part of the key are going to be thicker than a key without a transponder. This is not always the situation, but it is a good indication. One more test is to roll up the plastic part of the key with multiple layers of tin aluminum foil in order to then try to start the car. In case it does not start, there is a transponder there. There are a few exceptions to this guideline, but not many.
An additional indication that you have a transponder key is if it is expensive. Call your locksmith with your VIN number and inquire how much a replacement key will cost. In case it is a couple of buck, possibilities are strong that it is certainly not a transponder key. If it is over $100 or sometimes over $300, you can be sure that a transponder is present! Again, there are some exemptions, but not many.