that diagram is pretty poor as it does not present the nescessary information, it leaves you to puzzle a few things out.. however assuming that "square" where the three yellow wires congregate is a relay then this forms a crude immobiliser system. the yellow wire for the "ignition key switch" hijacks the output from the ignition barrell for the IGN position. Then replace the coils +12v feed with the thick yellow wire labelled ignition coil. the thin yellow wire goes to the ACC output of the ignition barrell.
Picturebook edition with lift-up-flaps on request
