siIN00Hatch

00 si, in 00 hatch, wont start, cranks but wont start. what i have figured out with a volt ohm meter is that my ecm is not telling the injectors to open. i switched ecm's, same thing. what i need to know is what sensor tells my cpu to open the injector, where its located and how to test it. is it a cam angle/position sensor? and which pinouts on the ecm go to it or them? are there two?(intake and exhaust?)or does something else like the crank angle sensor tell the ecm to tell the injector to open? thanks for reading this, any help would be greatly appreciated.