If it is the passlock system, would the light in the dash light or flash? My light turns on but then goes off after a little while (matter of seconds)could be the crankshaft position sensor. Could also be the Passlock system, if you have a known good ICM and CPS. This happened to my 99 Burb a couple years ago, only sure cure was to have the function deleted in the computer. $250 but he starts when he's supposed to!
The ICM is a few days old, bought a brand new but still no guarantee that its working properly.
New CPS hopefully arrives today.
Is there any need for some learning process after?