The 2012 kia optima fog lights not working causes are corrosion and failed relay. being able to see at night is important for driving down the road. your lights need to be working or you may get into a wreck. some issues will show up at some point. a faulty wire could come about. lights may burn out prematurely. corrosion is very nasty to deal with. blown fuse can come about. a failed relay equals a failed light source. these issues need to be dealt with quickly. the light bulbs will stop working eventually. if it becomes dull, you will have to replace them. they aren't that expensive, so they won't hurt your bank account.
If the headlights or turn signal on the 2012 kia optima is not working then you may have a bad set of wires, burned out bulbs, or a blown fuse.