For the record, I've rewired my O2 sensor a couple years ago because I lost the wire connection in the engine bay. At the time, I cut the 2D wire (black), which I was told to be the O2 sensor wire.

Right now, I'm attempting to add grounds to the ECU. When I unwrapped the tape on the harness to get to the soldered joint where all the ground wires are joined together, I find that the 2D wire I cut a couple years back was part of the ground joint!! My 2C wire is brown/black by the way.

I've read before that some older models have a different wire color, but I can't seem to find that post again. Can someone please confirm for me that my ground is 2C (Br/B) and O2 sensor is 2D (Black)?

 

2D is grey and is for the 02 sensor.

2C is brown/black and is a ground for the sensors.

Originally the ground for the shield of the 02 sensor was pin 3G or 3A or 2R. They are all tied together and are grounds for the ECU and terminate on the top of the rear rotor housing. I'd use one of those wires for the shield termination.

 

My aftermarket O2 sensor (crimp connector) doesn't seem to have a shield, how will shield grounding work? Will the sensor mounting point be good enough a ground by itself?

 

The shield was a part of the cars harness. It is not a part of the 02 sensor harness.

You could just run a plain jane wire from the 02 sensor to the pin 2D on the ECU.

The Shield on the original harness did NOT ground at the 02 sensor. It grounded about six or so inches from the ECU plug. Where it was grounded, was inside the wrapped harness. It was spliced to pins 2R's wire, and some other ground wires. The shield was for protection from EMI.

The 02 sensor will work without the shield or the shield being grounded if you have a shielded wire.. As long as you don't ground the center conductor in any way it should work. The center conductor on the shieded wire was grey in color.

Yeah, the 02 sensors base is the ground for the 02 circuit. FYI the 02 sensor puts out the voltage. The voltage is way below one volt dc. It's measured in milivolts. So for sure you don't want to ground out the single wire from the 02 sensor to the ECU plug in any way.