2004 gm Buick century dash lights security light flashing.
Question = car wont crank start battery start cable wires are fine, except for security light flashing car will start after i leave the key in the ignition for few seconds.
The flashing security light is the problem. You may have a problem with the ignition lock cylinder causing the theft system to prevent the car from starting.
Leaving the key on is basically letting the system relearn the security code. There are also wiring connector problems on this Buick in the underhood junction block that can cause this.
This is all assuming you do not have a non-factory alarm or remote start installed, as these can cause problems with the factory theft system.
The security system on todays cars and trucks prevents the vehicle from being stolen. There are many variations of the system going back to the early 1990's.
This warning could be on when the engine is running, indicating a fault has been detected in the system. If left un repaired, there is a good possibility that the car will eventually not start.
There are several different possibilities for the cause of the warning, depending on the make / model / year of the vehicle. Anything from a bad ignition cylinder wire, to a bad cylinder to a dad Body Control Module (BCM).
After market (non-factory) alarm and remote start systems can cause havoc with the factory theft system, causing this warning light, or a no start.
2004 Buick Century Security Light On Dash