Yeah , I would do an auto scan and record all the codes of all the modules before disturbing components and generating new codes. Check TSBs .See what similarities the codes between different modules share with one another. Look at power and ground distribution to see where the shared power flow and grounds originate and end. Power goes into the Integrated Power Control Module (Basically the engine compartment fuse and  relay box.) Do not jam test lights tips into relay terminals that can spread terminals and cause connection  issues.
   Don't guess and change parts that will have you married to something.