Some Help Please. I was having an O2 sensor problem where the code was showing, but no CEL. And the O2 is brand new. I started looking at the wire harness and came upon this: There is a grey uncovered wire coming from the O2 sensor wire, into a black and red wire, another wire from the red and black into a set of wires. Are these wires possibly grounds? I'm stumped on this, and wondering if this was done for a reason? Any help is appreciated. I believe the Harness is SI considering the engine is sohc non vtec ZC, and a pm6 ecu.