Ignition problems
 

My 2000 2500 6.0 Silverado has done something twice that I can't figure out. When I turn the key it turns over, fires and then quits immediately. It did it the first time one morning when the engine was cold and it didn't crank until I got home that afternoon and it fired up like nothing happened.
Today, I had parked at the NAPA and it was shut off for about 15 minutes. When I turned the key, it did the same fire up then quit. I pulled the battery and took it into the store and had it checked; good battery. Put the battery back in and turned it over a couple more times after the fourth or fifth time it fired up and then I got a SECURITY message in the message center.
I was thinking if it wasn't the battery it had to be the fuel pump but the SECURITY message I don't understand. The truck is new to me ( got it used for cheap with 114000 miles on it,so it is worth putting a little cash into for me) and I don't have the factory keys with it. Could that be part of the problem? I didn't know if maybe I should try to get the factory key (are they smart keys?). I was also wondering if maybe the ignition switchmodule was bad.
Any ideas would be greatly appreciated.
Thanks!

RE: Ignition problems
 

tuff problem to diagnose,i'd take it to a dealer before some hack tosses parts at it un-needed.

most likely,its the pass*key sensor,which requires a new ignition housing and harness.expect to pay in the 300 dollar range for parts,and about 3 hours labor if thats it.