Transponder Keys for Vehicles Explained

Almost every car comes with a transponder key today

Almost every car comes with a transponder key today

Almost all new cars on the road today come with some type of “transponder key.”  Toyota, Ford, Chevrolet, Chrysler, Nissan, BMW…. Most every car manufacturer uses a transponder key.  I hope this post will help you understand more about them.

What is a Transponder Key?

Simply put, these keys have an rf transmitter inside of them.  A device near the ignition switch of the vehicle has a receiver.  The key transmits an extremely low-level signal that the vehicle can detect only when the key is in the switch.

Why Do Manufacturers Use Transponder Keys?

They are used to prevent the car from being hot wired.  The car will not start if the device at the switch does not detect the low level signal from the key.  If a copied key is used without the proper signal, the car will not start.  If someone tries to hot wire the car, the car will not start because there is no signal from the key.

How Can I Tell If I Have A Transponder Key?

In most cases, the plastic part of the key will be thicker than a key without a transponder.  This is not always the case, but it is a good sign.  Another test is to wrap the plastic part of the key with several layers of tin foil and then try to start the car.  If it does not start, there is a transponder present.  There are some exceptions to this rule, but not many.

Another indication that you have a transponder key is if it is expensive.  Call your dealer with your VIN number and ask how much a replacement key will cost.   If it is a few buck, chances are strong that it is not a transponder key.  If it is $50, $100 or sometimes over $300, you can be sure that a transponder is present!  Again, there are some exceptions, but not many.

What Does This Have To Do With Remote Car Starters?

In their most basic form, a remote car starter is “hot wiring” your car in a very precise and controlled way.  If the car does not detect the signal from the key, your remote starter will fail to start the car.

How Do You Get Around This?

There are a multitude of devices that are available to bypass this issue during remote starting.  These devices fool the car into believing that the key is present.  It is important to note that this is only happening during the remote start cycle.  We do not, in any way, remove the protection that the transponder key provides.  We simply bypass it during the start cycle?

Do These Devices Void my Warranty?

Quality bypass devices installed by a professional will not void your vehicle’s warranty.


Mobile Edge has been installing remote car starters long before transponder keys were available on any car.  We are aligned with the best manufacturers of bypass modules and know how to install them correctly.  Stop in anytime with your vehicle for a firm price quote on a new, high quality, remote car starter system.


    • says

      Absolutely… I can’t think of any vehicles where the factory key would cease to work after a quality starter is installed properly.

  1. Rich Martin says

    I have a question. If I have any transponder, can I stop it from being read if I put it in a tin can and put the tinc can’s cover on over it? Can I also do the same ting by wrapping the transponder in tin foil? Tanks in advance for your answer.
    Rich Martin

    • says

      In most cases, wrapping a key in tin foil will cause the key to not start the vehicle. I can’t say this across the board, but I believe it to be the case for most transponder keys.

  2. K Dog says

    We recently bought a 2001 F-150 ( has a transponder key) came with a remote start when trying to start with remote it cranks the engine but will not start. It will continue to crank the engine until you push stop on the remote. What could cause this?

    • says

      Kenny, This could be any number of things: Tach, transponder, or a bad module to name a few. This is something you would definitely want to find a quality facility to troubleshoot and diagnose your issue.

  3. says

    Thx Mitchell, Your explanation of transponder keys was informative and helpful and leaves me with only one question. You say that wrapping with tin foil can determine if a key has a transponder. Most people don’t have tin foil as a usual household item, so, will ALUMINUM foil do the trick?

  4. says

    So then movies are lying all the time! I’m kidding, I already knew that! But I did not know about transponder keys before. It makes perfect sense that all cars should have these things. Good read, and helpful in understanding more.

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