You can find that info in the FSM. There are chapters in the wiring section for connector locations & splice locations.
The wire it looks like you are chasing is the 12v input to the coil. That one splices & also powers the injectors. If the injectors are all getting 12v & the coil is not then it is likely a bad splice (from the diagram it looks like at S-128 between the #2 & #3 injectors goes to the coil) or the wire from there to the coil.
See online read only FSMs here:
Jeep Knowledge Base
You may have to go to the bottom of the page & pick Jeep Resources & online manuals if it directs you to home page rather than the knowledge base.
Pick your model & year then on the drop down menu pick the chapter you need.