need stock O2 wiring help (with pics)

[dreamweaver13]

I was putting my car together after a compression and leakdown test. Barely touched the stock O2 wiring connector, and one of the wires fell off.
I took apart the connector and was confused by the wiring. There are 3 wires going into the connector from the sensor. But there are 4 wires coming out of the connector. The Wiring Diagram shows this as well. There is the signal wire and heater wire to the ECU plus 1 ground that ties into the +B ground on the ECU. There is also another ground. I'm just wondering how these 2 grounds are supposed to connect at the connector. My wiring must have been screwed with by a previous owner.

 

[MDCmotorsports]

IIRC the brown is the signal wire.

There are 3 wires on the o2 sensor. Two of them are the same color. Those are power. They can be crossed with each other.

The color wire on the o2 sensor is the signal. It has to go the signal wire on the harness.

 

[dreamweaver13]

thanks for the help guys. I probably would have saudered the signal wire to ground and then wondered why it wasn't working. The wire around the signal (brown) wire still confuses me though. Why is the signal wire wrapped inside a ground wire?

 

[dreamweaver13]

that makes so much sense now. Thanks for the info

In the process of taking apart my O2 connector to fix the signal wire, the clips that hold in the terminals fell off. This connector has definitely seen better days. Now I'm trying to find a suitable crimp tool to assemble the Summit open barrel type pin terminals I have.