To reset your guest key, first locate the reset button on the back of the key fob. With a pen or paper clip, press and hold the reset button for 10 seconds. Once the key fob is reset, you will need to delete the old guest key from your vehicle's system. To do this, open the driver's side door and hold down the lock and unlock buttons at the same time for about 10 seconds. The horn will sound once the key has been deleted.