What is what...

^^Very first thing is go to MyMopar^^ You can download both a service manual and also aftermarket/ 3rd party "2 page" diagrams which can be easier ot follow but not as detailed or complete, and sometimes leave out connectors or options.

What is it you are referring to in your question? Is the lighting / engine bay harness there? Is the plug you are referring to the firewall/ bulkhead connector?

A photo would likely be helpful