2002 Chevy Malibu ingnition lock cylinder replacement

Electrical problem
2002 Chevy Malibu 4 cyl Front Wheel Drive Automatic 160k miles

i have replaced the ign lock cylinder. the instructions indicate i will need a scan tool to complete the job.
instructions state after replacement the vehicle either would not start or would stall. my vehicle started right up and i have driven it for a week.
the problem i have is the "theft system" lite stays on.
the instructions state, there are 2 versions of a relearn procedure that must be don in order to start car.
a 10 min ver or a 30min ver.
even though my vehicle will start, i have attempted the relearn procedure. however my system fails to turn off the "theft system" lite . it will not do the procedure.
any thoughts ?

thanks
Bob