Gen 3 O2 compatibility?

[jbueckert13]

Hey everyone,
Just got my ls swap running in my 1983 Fairmont (Gen 3 6.0, 823 heads, .600/.600/224/238 cam) and my o2 sensors only read between 440 and 450mv ish. I repinned each bank to a different sensor during the swap (passenger has a 4-pin, flat plug, and driver's has a 4-pin square plug). P59 ECU is from a 6.0 Yukon, dbw. My question is, do I need to grab o2 sensors from that specific car? From what I see on RockAuto and LOJ, the sensors are compatible from 2003-2007. Here is the base tune if maybe if it's the tune.
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Fairmont Base Tune.hpt

[Alvin]

I would double check pinouts. All of them work the same. They usually hang around 450mv unplugged or broken signal wire.

[SteelGreenStallion]

Some are internally grounded and some are externally grounded.

[blindsquirrel]

Is the harness also 2004 Yukon 4WD? The old case/isolated ground thing was purely down to differences in the harness, no difference in the PCM hardware or calibration.

That model does not have a case ground/isolated ground option, there is only one diagram and it's isolated ground. If you use case grounded sensors with an isolated ground harness, all that does is provide a second signal low reference circuit.

However, if it's using some unknown mystery aftermarket harness, then who knows how it's supposed to be hooked up.

screenshot.07-11-2022 20.22.53.png

[jbueckert13]

So, if I understand correctly, the 2004 Yukon ECU is an isolated ground system where the ground comes from the ECU for each sensor vs a common ground. I'll beep the 2 o2 sensors for continuity between the 2 grounds and that should tell me how it's wired. If it beeps, run the ground from each sensor straight to the correct pin on the ECU.

My question now is, if it is wired correctly, does it matter which o2 sensor is on it?

EDIT: I have been reading lots, and it seems the general consensus is that you cannot use black plug o2 sensors (case grounded) on 2003+ ecus/harnesses (isolated ground system) and vice-versa. I'll swap sensors to the grey plug 2003+ which will match my ecu/harness and report back

[blindsquirrel]

The PCM is the same with either setup, both PCM internal hardware and PCM software. The PCM does not know or care whether it's case/isolated ground. It's entirely down to the harness, and the harness determines which sensor type it should use.

[ohthatskris]

Grounding the low signal and ground wire of the o2 sensor to a solid ground connection also helped me.
But for my setup I also had bought case ground o2 sensors because that what my psi harness called for.

But I’d listen to blindsquirrel before u listen to me.

[jbueckert13]

Update: Apologies for taking long. I swapped it back to white plug isolated ground sensors and it works mint now. Lt1swap.com has good information on gm o2 sensors. The isolated ground sensors are the same from 2004-2013