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How to check a key FOB to see if it is working

Updated November 21, 2016

Today's keyless remotes -- also known as key fobs -- make life easier. No more balancing your groceries on the bumper fumbling with car keys or making sure every door lock is down. It can be particularly frustrating when your key fob stops working or starts to perform sporadically. Check your key fob to make sure it is in top condition so it will work when you really need it.

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  1. Take your key fob out to your car. Press the alarm button. If the car horn fails to engage, your key fob is not sending the proper signal. The fob must send a signal that is strong enough for the car to respond.

  2. Change the battery. All key fobs require a standard watch battery. You can have it changed at a jewellery store or change it yourself with a small Philips or flathead screwdriver. If there is a screw in the back of the fob, remove it, and pry the fob apart to reveal the battery. Replace the battery with the positive side up and snap back closed.

  3. Reset your fob if the battery is new and it still is not working. Since fobs work on a radio frequency, they often will be disrupted by another electronic emitter such as a electronic tollbooth scanner or an electronic payment device that is attached to your key ring. Instructions for resetting your fob will be included in the cars owner manual. Use the car's "programming" mode to reset your fob.

  4. Visit a dealership or an automotive locksmith if your key fob still does not respond, especially if it is under warranty. A reputable automotive locksmith will cost less if you have to replace the key fob. A key fob's buttons will wear out the electrical contacts with use. These can be repaired at home with an application of conductivity paint (sold at electronics stores) but only do so if you are used to working with electronics.

  5. Tip

    If you cannot find a small Philips head or flathead screwdriver, try the file on a pair of fingernail clippers. The end is just right for fitting into a small screw or prying the fob apart along the seam. If you do noit have your car's owners manual, programming instructions for your remote can be found online. Often car forums will contain the programming instructions.


    Since a key fob is attuned to a special frequency that is only detected by the car for which it was issued, you will need to have your vehicle to test the fob. Otherwise you will have to take it to a dealership or an automotive locksmith to have them test for the right frequency. Be aware that repairing the key fob on your own will void the warranty. Check with the dealership if you are unsure about your key fob's warranty. Use a professional association to locate a locksmith. This will ensure that you get a qualified professional and eliminate your exposure to fraudulent locksmiths.

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Things You'll Need

  • Key Fob
  • Small Philips Screwdriver (optional)
  • Flathead Screwdriver (optional)
  • Watch Battery (optional)

About the Author

Susanne Koenig
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