LS6 - o2 sensors going crazy

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Apr 25, 2016 | 08:14 AM

Inflame

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LS6 - o2 sensors going crazy

I have an LS6 swapped M3 running F-Body Harness 99 F-body PCM, just got it dyno tuned and the tuner said the o2 sensors were oscillating erratically, making the car undriveable.

Any way, I installed new o2 sensors and that didn't fix the problem... I then crossed them to see what would happen and my theory of was correct, one side continued to get richer and richer while the other side continued to get leaner and leaner.

What would cause the o2 sensors to go haywire?

For example, with them plugged in correctly.

B1S1 and B2S1 would alterante in voltage and STFT
B1S1 = .8mV STFT 40% to .1mV STFT -40%
B2S1 = .1mV STFT -40% to .8mV STFT 40%

Would jump to roughly those #'s back and forth, within a 100rpm increment of where ever I hold the revs, VERY VERY similar to this thread which does not have a resolution posted.

https://ls1tech.com/forums/pcm-diagn...l#post15817850

Crossing the O2's, they were stabilized but like I said above, it would richen one side and lean out the other and continue in it's given direction.

Attached are screen shots of what I mean. I checked the wiring from connector to PCM and there are no broken connections.

Crossed O2 Sensors, B1S1 into B2, and B2S1 into B1.

Plugged in correctly, B1S1 = B1 and B2S1 = B2

Last edited by Inflame; Apr 25, 2016 at 08:19 AM.

Apr 25, 2016 | 10:20 AM

Inflame

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I should add that this, or something in unison with this is causing the car to buck very hard trying to accelerate.

Apr 26, 2016 | 08:15 AM

Chevy406

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What's the scale for your O2 volts? Can't tell if the O2 sensors are dead or just that the scale is killing any readability. Are these screen shots at idle or with a load on the engine?

Apr 27, 2016 | 08:13 AM

Inflame

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I did not do the tune, this was happening post tune. I talked to my tuner and he asked a few other questions and the O2 volt scaling came up so we believe it is that.

That is no load, probably 10% throttle tip-in, brand new o2 sensors.