Okay, I have a new 4-wire O2 sensor and harness. Is the purple wire the ground?

 

Purple wire is the "signal" to the PCM. Tan wire is the ground return to the PCM (your 93 will not have that pin in the PCM connector). Pink wire is +12V for the heater circuit. Black wire is ground for the heater circuit.

 

My harness has two brown wires and no black or pink so I wasn't sure what was what. Based on the schematic I'm using the outside brown runs to the 12V source, the inside brown is the ground, purple to the ECM and the tan is not used. Thanks.

 

Conversion to heated O2s diagram:




Normal heated O2 wiring:

 

That's the diagram I am using, but my harness isn't marked A, B, C, D so I was a little confused. I think I have it all in order now. Thanks again guys.

 

Rob:

Why does the conversion drawing show the brown wires for the heater element, while the 95 wiring diagrams on your web page show the black and pink wires for the heater element? I have an old stock sensor in the garage, and it has the brown wires, but I thought your wiring diagrams might be more accurate.

 

Yeah, I know. I modified the diagram above to match the real world harness plug that I have in the pic. It would have been confusing otherwise .

The PCM diagrams on my page are not modified and show the pink and black wires (probably where you saw it). I guess I should try to be more consistent.

I don't have a clue why the factory diagram does not match the harness colors for those two wires.

 

If you look closely, the harness plug has the letters molded into it. Most every factory plastic harness plug does. I added the typed in letters for clarity.