Blazer Forum - Chevy Blazer Forums - 00 with security light staying on

Sounds like the beginning of an ignition switch failure. If the ignition switch doesn't see the programmed key, the security system will be activated.

Here is the passlock relearn proceedure:

Quote:

30 MINUTE RE-LEARN PROCEDURE

[ol][*]Turn ON the ignition, with the engine OFF.[*]Attempt to start the engine, then release the key to ON (vehicle will not start).[*]Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.[*]Turn OFF the ignition, and wait 5 seconds .[*]Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the PASSLOCK(TM) Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK). IMPORTANT: The vehicle learns the PASSLOCK(TM) Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.[*]Start the engine (the vehicle has now learned the PASSLOCK(TM) Sensor Data Code and/or password).[*]With a scan tool, clear any DTCs if desired (history DTCs will self clear after 100 ignition cycles).
[/ol]

If that doesn't work, you may have to go to the dealership and have them program your keys again, but if the ignition switch is going out, it may not work either...