99 blazer starts then shuts off
1999 S10 Blazer 4.3L, 4dr 4WD. Truck starts but immediately shuts off. If I dribble gas into throttle body continue s to run. Suspected a passlock problem but the security light comes on when key is turned then goes off after a few secs. Start the truck it starts then dies, then the security light comes on for 2 secs then blinks one time then goes off. I pulled the ignition lock out and unplugged the passlock connecter on the ignition cylinder housing. used a screwdriver to rotate the ignition switch and get the exact same results. starts and dies one blink on security light. Anyone ever come across this failure before?
Thanks for any help or suggestions.