Hey so I bought a 91 crx si about two weeks ago. I got about 20 mpg so I checked out my o2 sensor. It's not even connected to anything. There's a black wire coming from the back of the o2 sensor and I don't know what wire to connect to on the harness. I have a d15b7 in there that someone swapped in before i owned it. Everyone is saying that the o2 sensors are usually a white wire and you plug it right into the black wire. My problem is... There isn't a white wire. There's only a green and yellow one sticking out of the harness, cut about 1 inch from the wire loom. So is this a normal color for the o2 sensor to plug into or should I rip apart the loom and try to find a white one? By the way I don't know if they changed the harness or not when they swapped engines. Doesn't look like they did cause I can see a few places where they spliced wires to make connections work. Any help would be great thanks.

 

I recommend upgrading to the O2 sensor from a 93 Honda Civic VX.

Moar wires.

 

You may have to trace the wire back from the ecu since it appears your harness may be chopped up some.

 

So I ohmed it out to this random wire hanging around and found it after a lot of digging it ended up being a black wire. So I cut it back and it's one of those wires with two wires in it I'm guessing ones power ones ground or something cause theyre separated by a rubber sheath. Am I good to just splice the two to the one wire coming from the O2? And yeah I'll definitely upgrade I just wanted to get my car getting more gas milage than a bus!

 

you cant just swap a vx o2 sensor in, you would need the vx ecu, an egr and a ton more work.


if you found the correct wire the outer sheath on that wire is a ground, the inner is the signal to the ecu.

 

So should I splice them both together to the one wire O2? Or should I ground the one wire to somewhere on the frame and splice the one signal wire to the O2? Sorry if that's a dumb question but my cars still acting up

 

the signal wire is for o2 sensor signal. the ground is to shield that signal from interference. it SHOULD be already running to the ground on the thermostat housing.

Your wiring diagram should also show this.

 

On the harness side of the o2 wire, how far does the shielding go, all the way to the plug? Mine stops back where the wire enters the loom with the rest of the wires in the harness, is this correct?

 

Yeah that's how mine is like that too