What does this wire do ?

Yeah I know , I'm going through this car and its like I see , I fix and go back to what I was working on .Ive gone thru the entire engine compartment and cleaned everything as far as contacts . I'm going crazy trying to troubleshoot the charging problem . My daughter printed the wire diagram out both pages. I then taped them together and traced out the wires with high lighters which was a huge help . Having ADD DOESN'T HELP ! Lol but I know now the wiring is good and wont be a problem in the future so I'm going to replace the hacked wire and hopefully she will charge .