How do you reset fob key 2013 optima

This works with a lot of makes: Get a new battery, then from inside the vehicle open the case and replace the battery in the fob then start the vehicle. I have done this to a least a dozen vehicles and have never had a problem.

If you allow the fob battery to run so low that the car no longer recognizes it, the car might not respond to the fob after you replace the battery. In that case, follow instructions in the owners manual for reprogramming the car to the fob. If the fob is still recognized and you get a message that the fob battery should be replaced, the best procedure is to do this within range of the car so the car doesn’t lose the code to the fob in the process. In most cases you can replace the battery while away from the car, but why risk it?

If you're talking about programming a new fob to the vehicle follow the instructions that came with the fob, check youtube for a how to video, or visit your local locksmith. Usually just replacing the battery doesn't cause a problem. Hope that helps! Jim