Which wire connects the o2 sensor
 

I've got a black/white and a black/green wire coming out of my harness,
But only 1 wire from the o2 sensor.
How does the o2 sensor wire up?

it should hook into the green connector, it's kinda tube shaped. Mine is spliced to fit a Bosch sensor.

That connector's gone. I just have the 2 wires. How do those wires 'wire in' to the connector?

The 02 sensor wire connects to a connector nearby. This connector is attached to a grey colored cable. This grey colored cable is a shielded connector with a BLACK center conductor. The 02 sensor wire gets connected to that BLACK center conductor wire. There is a shield around that black wire and you want to make sure the wire strands of that shield do not touch the center conductor/02 sensors bare wire.

On a series four the connector WAS green in color. Yours is gone so....splice the 02 wire to the black center conductor wire.

I tried the black w/yellow stripe wire and the larger black w/white stripe wire, and got 0 voltage to either when connecting the o2 sensor. Is one of those wires supposed to be grounded?

bump

Most all black/yellow wires are power wires. Most all black/white wires are switched power wires also.

On a series four car the middle plug on the ECU has the 02 sensor input wire. It's pin 2D on the bottom row of the middle plug. Bottom row...middle plug.......second wire from your right as you count from right to left when looking into the wire side of the middle plug.

That wire in 2D is pure black. IF you unwrapped the harness and followed that black wire up the harness you'd find it comes out of a grey shielded cable. The shielded cable has a mesh wire inner wrapping that is the SHIELD of this shielded cable.

On a series four the other end of that shielded grey cable exits under the rear of the intake manifold/throttle body area. On a series four turbo it exits near the thermostat if memory serves. Not sure.

Middle plug...........bottom row.......second wire from the right when counting from right to left.