See the diagram in the site thread below.Click for GVR4 thread
It's a big fanout sheet for 4g63 type wiring. Pins with the little circles drawn around the wires, for the 02 sensor and the knock sensor are a shared shield setup; open an unattached at one end, connected at the other, but not part of a circuit - just noise/RF rejection, likely only could be causing by radios/plugs/etc.
I just build a little harness to replace my current one should anything in it go bad, and I had my hands on those wires first hand. The other guys before me, nailed it!