1999 tahoe passlock issue

[c10 custom]

hi guys i am working on a 1999 chev tahoe and it has the passlock issue
it turns over great but olny runs for 5 seconds then shuts off security light is on
i changed the ignition switch and the part that contains the passlock sensor whitch is the part that the lock cyclinder goes into not sure where to go from here i tried the relearn procedure turn key to run position for 10 minutes then back off then tried to start and nothing any help would be greatly appreciated thank you