How do you fix the security ligh on a 1999 Chevrolet lumina and what does it mean?

Answer 1

It means that the car is not able to recognize the chip that is in your ignition key. This is bad because usually with security features like that, the lack of the chip causes your fuel pump to shut down which means you'll be running on only the fuel already in your lines.

I had this happen on mine only once and a gentle wiggle of my key made the light go off. You can also try cleaning the key with rubbing alcohol to get rid of any grime that may be preventing the chip from being read. It's something worth having a garage take a look at.