I see this question of "how do I know which is the ground on my vtec oil pressure sensor??" come up alot in here. and there's not an easy way to describe it. So I took a pic of mine (which vtec worked when I was done). This was for a 1999 y8 Head, I looked at a 1995 Z6 oil pressure sensor and it was the same wiring. these are 2 of the 3 wires you need to run, the 3rd wire is to the vtec silenoid and there is no ground so it will be hard to mess that one up. hopes this helps anyone doing mini-me! (The ground wire is on the opposite side of the 2 plastic grooves) then I filled the end up w/ silicone to make it weather proof good luck!