My 2004 Saturn ION shuts down the engine when I turn on my headlights or turn on

The direction I would take would be to check my powers and grounds, mainly grounds, on the Body Control Module. It sounds like the BCM is using the ground through the light switch until the light are turned on and the ground is taken away. I worked on a car that used the ground through the wiper motor until the wipers were turned on. The body ground wire was ultimately the cause. It had corroded and broke in two.