The "Engine Control System" section of the FSM has all the codes
https://www.nicoclub.com/FSM/Pathfinder ... der/ec.pdf
For fuse locations you can look in the "EL" section of the FSM or search google for 1999 Pathfinder Fuse Diagrams
Also, the older Pathfinders have known issues with the strut towers and the area around them rusting and rotting out, you might want to take a look if you haven't already.