O2 or lambda sensor wiring

[ABV-VR6 12]

Today while working on my car, I was inspecting my wiring before doing a clean up and noticed that the wiring for my o2 sensor had a wire broken. The yellow one at position 3 looks like it was ripped off the connector. A piece of wire was solder to it but instead of rewiring to the connector it was left aside with electrical tape at the end. 

So I'm wondering, on a VR6 engine do all four wires are usually connected, probably right? What would be the reason of cutting and isolating the yellow wire then? 

Thank you! 

[Dox 23]

I don't know in this case, but usually a 4 wire lambda has 2 wires for its inbuilt heater (they work better when hot) and 2 wires for signal (ECU). I suspect the 2 gold plated terminals are the signal to ecu connections.

 

 

[Dox 23]

The white wire to connection 4 looks narrowed like the wire is broken inside the insulation?

[1xshaunx1 27]

Where does that plug in. 
Agree with Dox, I think you should do a repair on 3 and investigate 4 it doesn’t look very well

[ABV-VR6 12]

Thanks to both of you! 

I investigated the white wire which indeed looked narrow in my picture. But it was just the angle and I guess dirt that made it look like it. 

What I've found is :

PIN1 : red & white is the power coming from the fuel pump relay. 

PIN2 : brown and goes to ECU 12 (sensor 1 heater ground). 

PIN3 : yellow goes to ECU 42 (sensor one ground and shared for both sensors late 94+).

PIN4 : white to ECU 20 (sensor 1 ground). 

So if my broken wire is a ground, then it should definitely be fixed. Funny thing is, there was no red lights at all when I last parked the car. You would think a lambda sensor is sensitive to that. I will fix it for sure, I was just curious as why the previous owner had not fixed it, seems like there was an attempt but then why adding an extra wire to just put tape at the end of it? I guess I'll never know!