1992 Cadillac EL Dorado wont start

Most common fault associated with a theft warning is a failed ignition lock cylinder. The electrical portion that is responsible for transmitting the ignition key pellet value to the theft module. A faulty(worn) key can also be at fault, so try another key if you have one. Most, if not all cases, the wires break at the cylinder, and the cylinder needs replaced to properly repair it. Although some have been successful in bypassing the system with resistors of the same value as the key.