Oxygen sensor ground location?

Sorry about starting a new post, but the title of this one is a little more clear and related to what I need.

In an effort to track down why my o2 sensors aren't working, I've started looking for a ground that I'm told is somewhere behind the engine. It supposedly has an orange wire. My car had an engine swap before I bought it, and I think it's very possible the ground was never connected.

Does anybody know where this should be? I don't see it anywhere. I'd like to know where the ground itself is, and which harness the wire came from.

Thanks!

I've checked around there and can't find it.

I searched another forum and found that that very orange wire passes through the big white wire connector the sits on the back of the upper intake. Sometimes referred to as the salt shaker since there is a similar black one right next to it.

I can see the wire there. I'm thinking I could just cut that wire and solder an eyelet on the end of it and make the ground myself. I just don't know if the side that needs to be grounded is the side going into the top of the shaker, or coming from the bottom. I suppose I could cut both and ground both to the same point.

Does this sound like a good idea?

Wait, if this is just the ground for the heater, couldn't I just test the heater by turning the ignition on while the car is cool, waiting a few minutes, then feeling the o2 sensor for heat?

Really? I know it passes through the white one. How far from the white one does it come out? This is really driving me crazy.

Thanks guys, I found it. It was covered with a shield so I couldn't see the orange. I traced it down to the bolt, where it connects to the braided wire that goes back to the firewall. I can't see it to tell how it's grounded, because I was feeling my way around.

Oh well, that's not my problem. Bummer.