I disagree with Pizzaguy about the siren. When those sirens age the internal batteries leak and the resulting corrosion on the board can feed back into the anti theft system which will prevent the car from starting. The anti theft system locks out the starting as it is intended to do should someone jimmy open a door. The batteries do not often cause this problem, but on occasson it has happened. Several members on this forum have been told their SKREEM module is bad after they could not get their car to start. They pulled fuse #9 reset the codes by pulling the battery cables for a minute started their cars and drove away. I am not saying it is a common problem, but it has happened, and in the spirit of checking all possibilities, this being such an easy and quick process, it is foolish not to give it a try, I quote from the Chrysler Student reference book "The Vehicle Theft Alarm system sounds an alarm siren, flashes exterior lamps and disables the ignition system when the alarm is triggered." I feel quite certain a corroded corrupted board on the siren can trigger the anti theft system.