So I am putting my car back to stock. And it's taking awhile, just cause of work and the car is at my parents. Right now the car doesn't start. It turns over but won't crank. I've checked the flywheel positioning sensor and cleaned it with some carb cleaner, no luck. Any thoughts on what I should check next?

Also this is the last plug I can't figure out for the life of me where it goes:



It is connected to one main wire that is split into four sections. one of the wires goes to the power steering pump:



One goes to the alternator:



One goes to this:




So I can't figure out where that first one goes. Any ideas? And any idea of what kind of troubleshooting I should do next to get the car started?