2003 Monte Carlo security re-learn
 

I just replaced a lock cylinder and the 3 x 10 min relearn doesn’t work. The car won’t start but the security light is not blinking. HELP NEEDED

What prompted the need to change the lock cylinder?

Assuming the chip for the lock cylinder is plugged in all the way and no wiring issues, the only way to fix this is the security relearn. Attached is a document I keep on this (pulled from the GM shop book). It is important to watch that after 10 minutes the security indicator stops and that you never remove the key from the cylinder.

I waited 15 minutes for mine. Started on the 3rd try. Never took the key out.