Oscillating O2s

[filtercoffee]

Took a datalog of O2 sensors (attached) and I'm noticing some weirdness.

View post on imgur.com

See bank 2 secondary voltage oscillating, and primary also oscillating to an extent.

There are a lot of variables that changed so I am looking for some direction or advice on how to narrow it down. ideally in the way that requires least effort.

The current setup is Z4M stock tune with catless headers and O2 simulators. I just put the simulators in which is why I noticed this weirdness. Additionally I made a mistake and cut the bank 2 sensor 1 primary o2 signal wire, and soldered it back together as a fix. Bank 1 and 2 primary o2 sensors are new, having been installed this year. Bank 2 sensor 2 is a new bosch universal o2 sensor. I also noticed a pending P120D (excessive fuel injector flow bank 2) prior to my simulator work, but I cleared the code and it hasn't come back.

There are no codes (yet). One drivability issue which exists now and has existed is a subtle power oscillation around 3k at WOT but unsure if it's related.

What are some clever ways to narrow down if this oscillation is due to a faulty O2 sensor, fuel injector, O2 simulator, or the solder joint on B2S1?

PS if there are any pros who can help but want to be compensated for their consulting, feel free to reach out. I'm looking for opportunities to learn.

[filtercoffee]

update: I believe the secondary o2 oscillation is due to the cat simulator turning off and on (its led light is blinking at a similar frequency). I'm finding out from the manufacturer why it's doing that on one bank and not the other.

update: the led goes off when voltage from the O2 sensor goes below 0.45 V. the simulator is likely working as intended.

[pokeybritches]

How were the simulators wired? You need a separate ground for the simulators. The heater ground is switched by the ECU.

Do these simulators reference to the primary O2 signal at all, or are they simply signal generators that replace the secondary O2 sensors? Or does the simulator setup require you to leave the secondary O2 sensors in place, and the simulators wire in series with the secondary O2 sensor outputs so that they modify the output before it reaches the ECU (like a piggyback controller)?

[filtercoffee]

grounded to chassis.

these simulators leave the secondaries in place and intercept them in series. I cut the black signal wire from the o2 sensors and soldered them to the simulators. power is a 12V source from the fusebox (I ran a wire through the firewall) and the ground is a wire to a strut mount bolt.

so far it seems to be working regardless of the oscillation. the catalyst test passes and I have no codes.

I updated my post above your last one with more info from the manufacturer

Here's a fun theory! could it be possible the oscillation I saw is actually the ECU doing a test? like an o2 sensor response time test? I will check if the oscillation is still there next time I go for a drive.

[pokeybritches]

It could very well be the ECU carrying out the test, although the primary O2 sensor should be cycling too. I've seen the switching taking place on my own car at idle. It would cause minor fluctuations in idle while it switched between lean and rich conditions, and I could hear the changes in exhaust note. The ECU does some other tests too, like test response time during decel and acceleration. Hopefully that's all it is, but as long as you pass readiness, that's all that really matters

[filtercoffee]

Glad to know this could be normal! The primary sensor is cycling too, it's the green line in the original pic. Green and red are the two primary widebands, I believe.

[filtercoffee]

got a code today. P120D. anyone have access to more technical information about the trigger for this?

[Steeler]

https://www.engine-codes.com/p120d.html

[filtercoffee]

^ obviously googling is the first thing I did. That webpage seems pretty generic and did not have enough information for me.

Update. The code disappeared on its own after several drives. /shrug.
One day I'll pick up a windows laptop and tinker with INPA. Maybe it'll shed some light.

[maupineda]

Originally Posted by filtercoffee

^ obviously googling is the first thing I did. That webpage seems pretty generic and did not have enough information for me.

Update. The code disappeared on its own after several drives. /shrug.
One day I'll pick up a windows laptop and tinker with INPA. Maybe it'll shed some light.

Just go with ISTA+, much easier to setup and install and runs on win10