I recently replaced a lost key and FOB for my 2011 Hyundai Elantra. The key will make the engine turn over but it won't start. The old key works fine.

  • 2
    There is a LOT of information missing here. How did you replace the key and FOB? In nearly all cases today, a new one requires programming at a dealer or someplace that has the correct equipment for your vehicle. If you just bought one off the shelf somewhere, it likely is unknown by your car and programming is needed.
    – jwh20
    Oct 29, 2019 at 12:06
  • Thank you for this response. Now I know. I do not know why the dealer who sold me the replacement key forgot to mention it. Oct 30, 2019 at 19:08
  • Yes, that's odd because it's an extra service which means they will charge you for it in addition to the cost of the FOB itself.
    – jwh20
    Oct 30, 2019 at 19:33

1 Answer 1


Hyundai's outside of the US are equipped with immobilizer systems and new keys need to be programmed to the car. Since the immobilizer system is not accepting the code from the unrecognized key it is telling the engine controls to shut down the spark and fuel. To have the key matched you can call a local locksmith or take it to the dealer.

  • 1
    Why the downvote? This seems a perfectly reasonable answer, and likely the cause of the nonstart. Oct 29, 2019 at 14:54
  • @David Thanks for your comment, I assume someone is/was upset with me about something outside of the answer.
    – narkeleptk
    Oct 29, 2019 at 17:39

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