Is this security?

I have '99 gmc savana. I left it for about 3 months over the winter then tried to start it before it ran fine now it's crank starts and stalls after about 2-3 seconds, the security light flashes then goes out. I cleared the fault codes for the evap then tried to reset it to a new key that was cut by the vin. ?#1 does this have a chip in the key? The replacement was just a simple key, i was told that it senses the tumblers which in turn has something to do with the sensing?? I tried to "reprogram the passlock" by clearing all codes then crank, start, stall 10 min wait, again x2. But as described the security light doesn't stay on for any time more than 3 seconds. Fuel is good, new filter hot wired the pump to continue fuel but still the same. good pressure 50lb+ on the rails. It ran as long as i was spraying starter fluid in the throttle-body. Any ideas???

Yes folks it was the pass-lock $450 later. They say it was the modual now the security light says on.... they say the 2nd problem is the sensor and it has to be replaced. It seems that people only post messages here to get their problem solved then they are gone. Folks If we want to continue to fix our own rigs we gotta support each other. They are winning

yes they are. sorry to hear about your gmc I am having the same problems.