02 sensor bank 1 voltage drops in open loop

[Lsx_Power-parts]

Im needing help figuring out why my bank 1 oxygen sensor seems to be dropping voltage and spiking back up. Ive been tuning my ve recently in open loop and noticed just the other day this is happening. Does anyone have any suggestions on why. Ive suspected that maybe the oxygen sensor has went bad even though its new but it seems to be showing correct voltage key on engine off and when first started rises like normal but for some reason it drops in volts at certain speeds indicating a lean condition only on bank 1. My wideband is in the bank 1 exhaust pipe and does not seem to be showing a lean condition as the data log shows and I do not have any DTC's showing up either. Any Suggestionsknock retard.hplknock retard.hpl

[5FDP]

The o2 sensor will kinda just do whatever they want at part throttle when it's set to open loop only. They may only react when you go wide open throttle.

I will say this though, you did leave the short term fuel trims active and if you did any wideband tuning with a wideband error with the STFT still working, it threw off your data. The LTFT and STFT must be disable in open loop when tuning with a wideband.

[Lsx_Power-parts]

How can you tell my stft are active they aren?t active in my tune and my logs aren?t showing any changes to them other then when I enabled closed loop towards the end of the log to see how the sensors would respond

[5FDP]

Maybe it's just that log but the STFT did come on when the fuel system status still says OL.

2020-08-30.png

[Lsx_Power-parts]

Yes that was towards the end when I commanded closed loop to see what o2 sensors would do I?m confused as to why bank 2 in open loop is reading normal 900s mv but bank 1 readings are up and down periodically towards the beginning and middle of the log before I commanded the closed loop

[bk2life]

Im confused as to why bank 2 in open loop is reading normal 900s mv

yup, and so are we, and since this was never updated, we will never know..
and here i am with the exact same issue, and voila' nothing....

[slarsen47]

Old thread but seems like a good place to talk about O2 sensors.

Here is a screenshot that shows open loop but still with voltages.

Front sensors are connected but in open loop................still showing voltages.

Rear sensors are removed.................but still showing voltages.

Are the front O2's still heating up? Doing their job but not affecting anything?

Why are rear O2's still showing voltage even though not installed? Is the 0.450 v just a default in the PCM?


Screenshot O2 volts.jpg

[blindsquirrel]

That ~450mV is called 'bias voltage'. PCM is looking for a deviation from that point - lower is lean, higher is rich (and it assumes 450mV and never changing means dead sensor).