The only wire that looks like that that I recall is the coil pack/sensor ground wiring. I don't remember mine making it that far in the harness, and looping around, though.
------------------------------------------------------------------ 1992 300ZX NA 5 Sp (Dead) 1990 300ZX NA Auto 2+2 (Dead) 1990 300ZX TT 5 Sp (Building) 2004 G35 Sport 6MT (DD)