GMC Forward Control P3500 (1985-1999) Back-up lamps circuit, commercial chassis

A/T BRN WIRE HOT IN RUN I/P FUSE BLOCK LEFT BACKUP LAMP LT GRN WIRE M/T PARK/NEUTRAL POSITION (PNP), BACKUP LAMP SWITCH (LEFT SIDE OF TRANSMISSION) RIGHT BACKUP LAMP TURN B/U FUSE 5 TURN SIGNAL FLASHER