My Pontiac G5 2007 SE has factory remote start. The option for remote start is turned to on in the DCIM menu. And yes I've tried turning the key to the run position and back to off twice to reset the timer lockout on the remote start. When I try and use the remote start. The engine will turn over and fire up... For about two seconds. Then it automatically kills the engine. Any ideas. Please help!!!

SOURCE: 1997 pontiac sunfire key wont turn in ignition

You will have to have the ignition cylinder replaced in the car. The only thing that keeps that ignition from turning is a little tang on the sdie of it. The only way that tang moves is by the tumblers inside the cylinder moving it. They will have a hard time replacing it too as they can't remove the cylinder from the bore until it is in the "run" position. Obviously there are ways to get them out but it usually involves using half the tools of a good tech's toolbox. if it is towed the towtruck driver will have to use dolly wheels or remove the shifter cable at the transmission to get it to move as it will be stuck in park- unless is a standard shift.
I am sorry for the bad news. Get a second opinion from somebody that can put their hands on it , but it sounds like you have a tried all or most of the tricks.
Good luck...........Scott