At a loss on O2 sensor problem

[SaltMan]

Hi all,

I have a 97 Camaro with an LT1 that has been 411 swapped. I've been in the process of having it tuned and there is something wrong with the O2 sensors/wiring that I can not figure out. The O2's don't fluctuate in the log, one sticks around 8-900 mv, and one sticks around 0-100 mv, but also sometime they'll work fine for 20 seconds or so but only at idle. Car runs pretty good in OL and PE, but as soon as it goes into CL it runs like **** under part throttle. I've been doing a lot of reading on whether I have case or isolated grounded O2's, and from what I understand they are case. I replaced both O2's thinking that could be the problem, to no avail. Wires are going to correct pins, the only thing I found different on any schematic is that tans need to be tied into blue 63 on isolated ground O2's. Mine tans are not but I don't believe I have isolated grounds anyway. Any help would be much appreciated! TIA

[blindsquirrel]

That is the classic symptom you get when the O2s are swapped bank to bank. In the log, B1 trims are at -30 while B2 sensor is pegged lean, B2 trims are +50 with B1 sensor pegged rich.

[SaltMan]

So basically B1 is actually reading B2 exhaust and vice versa? I'll try swapping connectors and see if it helps in the morning

[blindsquirrel]

Yep.

Also could be injector wiring, the PCM adding fuel to the wrong bank would give the same result. Something's crossed up somewhere.

Based on your 2002 Escalade OS:
Case ground:
screenshot.24-02-2022 02.09.21.png

Isolated ground:
screenshot.24-02-2022 02.09.17.png

To find out if your harness is set up for isolated or case ground, unplug the PCM and both (or however many you have) O2s. Check continuity on the harness side between pin 'A' at any O2 connector and an 'A' at any other O2 connector. Isolated ground will have continuity between all the 'A' pins (and also to/between PCM C1 pins 25/26/28/29/63) thru splice S114. No continuity between any of those pins means it's wired for case grounds.

To find out if a specific sensor is case or isolated, just unplug and check between pin 'A' and the sensor body (or chassis ground, if it's installed). Continuity = case, O.L. = isolated.

The PCM and OS is the same for case or isolated ground, only the harness and sensors are different (and should be matched).

[SaltMan]

BlindSquirrel you are my savior!!!!! Switched those 4 wires at the PCM today and the car drives like a dream!!! They were absolutely swapped bank to bank. Thank you so so much! You ended some long sleepless nights and about a week or note?s worth of stress. Again can?t thank you enough.

[FWD GN]

Yep.

Also could be injector wiring, the PCM adding fuel to the wrong bank would give the same result. Something's crossed up somewhere.

Based on your 2002 Escalade OS:
Case ground:
screenshot.24-02-2022 02.09.21.png

Isolated ground:
screenshot.24-02-2022 02.09.17.png

To find out if your harness is set up for isolated or case ground, unplug the PCM and both (or however many you have) O2s. Check continuity on the harness side between pin 'A' at any O2 connector and an 'A' at any other O2 connector. Isolated ground will have continuity between all the 'A' pins (and also to/between PCM C1 pins 25/26/28/29/63) thru splice S114. No continuity between any of those pins means it's wired for case grounds.

To find out if a specific sensor is case or isolated, just unplug and check between pin 'A' and the sensor body (or chassis ground, if it's installed). Continuity = case, O.L. = isolated.

The PCM and OS is the same for case or isolated ground, only the harness and sensors are different (and should be matched).

Thanks for this. Huge help!

[evilstuie]

Yep.

Also could be injector wiring, the PCM adding fuel to the wrong bank would give the same result. Something's crossed up somewhere.

Based on your 2002 Escalade OS:
Case ground:
screenshot.24-02-2022 02.09.21.png

Isolated ground:
screenshot.24-02-2022 02.09.17.png

To find out if your harness is set up for isolated or case ground, unplug the PCM and both (or however many you have) O2s. Check continuity on the harness side between pin 'A' at any O2 connector and an 'A' at any other O2 connector. Isolated ground will have continuity between all the 'A' pins (and also to/between PCM C1 pins 25/26/28/29/63) thru splice S114. No continuity between any of those pins means it's wired for case grounds.

To find out if a specific sensor is case or isolated, just unplug and check between pin 'A' and the sensor body (or chassis ground, if it's installed). Continuity = case, O.L. = isolated.

The PCM and OS is the same for case or isolated ground, only the harness and sensors are different (and should be matched).

I know this is almost 2 years old, but this is single-handedly the best post, explanation and solution to this issue I've come across! Thanks mate!

[bk2life]

I know this is almost 2 years old, but this is single-handedly the best post, explanation and solution to this issue I've come across! Thanks mate!

I agree