Security light ?
 

I just got a new to me GM K 1500, 6.5. When I start it and the dash lights all test on there is one that says security. It isn't there on my 97 , and I have no idea what it is or does , and what to do if it stays on after starting. Are there some anti theft factory things on this truck? and how do you able/disable them ? what to do if it decides to make the truck secure?
??

Year would be nice to know?
passlock is what you should have,relearn procedure:
http://my.cardone.com/techdocs/pt%2077-0011.pdf

The one with the security light is a 98 GM K 1500 .

Any luck with the link I posted?
The passlock portion applies to your truck.

It explains it well. Now as long as I don't loose the keys I will be fine. I hope this security thingy doesn't cause grief when I install a command start.

There are issues with that but thy can be overcome but it depends on the system you get.