ECU box ground.

Bewy said
Dartfreak,
Whatever. The idea of compressing a star washer between two surfaces is to force the sharp edges of the SW to bite into the metal for good electrical contact. Use as many grd wires as you like. I am simply saying they are not necessary electrically if a good grd connection has been made as described above.

Im sure it would work either way. You may be right it does work better with the washer between but in my mind seems like more surface area making contact with the fender would be a more secure ground. Just a friendly debate im not arguing or anything