[gopomyaw]

(Also posted over at e46fanatics.com, bimmerfest, and bimmerforums but trying here for increased visibility.)

1) Car is an E91 2009 model year with ~110k miles, N52 3.0L engine.

2) I tried to pass smog recently and failed with a P2096 code.

3) I took it to my mechanic and he diagnosed the car as likely having a partly blocked Cat on Bank 1. Very expensive replacement.

4) We decided to first replace the O2 sensors (since it was due anyway at >100k miles) and pray we can clear the monitors and squeak through smog.

5) I got the O2 sensors replaced, got an OBDII reader, and have been trying to complete the drive cycle but to no avail. Everything is clear except for Catalyst Monitor. And even for that, the "completion" count regularly upticks for Bank 2 but not Bank 1. So I'm captured the right driving style that should be able to clear the monitor.

6) I searched around and found jfoj's excellent instructions for running OBD Fusion. And collected some logs.

7) Bank 1 O2 sensor #2 is consistently high in voltage 0.85+V in idle and initially when driving at the 40-60 mph range; it eventually starts dropping down but usually only low 0.80s or high 0.70s. Not sure if the ECU has given up by that point on completing the Catalyst Monitor for Bank 1.

8) I see no other codes pop up. Unsure if not not completing the Catalyst monitor is equivalent to failing some self-diagnostic (like P2096) or if I can some how cajole the car into passing the monitor and move through the test.

9) See here for some logs from a couple of days ago:
https://drive.google.com/drive/folde...l3?usp=sharing
Diagnostic Report AfterStartup -- key in ignition, but engine off
CSV InitialIdle -- a couple min after car was turned on
CSV EarlyLowSpeedDriving -- some surface street driving before I got to the highway
... and then some more driving ...
CSV HighwayDriving1 -- several minutes on the highway
CSV HighwayDriving2 -- more time on the highway
CSV HighwayDriving3 -- finishing up highway driving and coming to a stop
CSV Diagnostic Report AfterHighwayDriving -- report right after highway driving
CSV WarmIdle -- several minutes after finishing Freeway driving
(HTML files can be downloaded and then viewed in-vivo by your browser.)

Thoughts?

Thanks so much in advance!!

-G

[PhaseP]

Do you have leak at the connection between down pipe and mid exhaust pipes? That's close to 2nd o2 sensors and connection flanges rust out.

[E92_William]

If the cat is indeed blocked or clogged Ive seen good results from running cataclean. I suppose you could get it to clean the monitor if you're sneaky and put an o2 sensor spacer on the rear sensor. Just gotta make sure it has the same look as the rest of the exhaust parts somehow so it's not noticed by the smog guys

[gopomyaw]

> Do you have leak at the connection between down pipe and mid exhaust pipes? That's close to 2nd o2 sensors and connection flanges rust out.

I can't be 100% sure, but my mechanic, who is quite trustworthy and capable, has been pretty clear there are no leaks in the system. He intimated that if there was a leak the other monitors would be giving clues to that effect. Unfortunately I don't understand these systems enough to know what I'd be looking at in the ODBII scan to see if there is indeed an airleak.

> If the cat is indeed blocked or clogged Ive seen good results from running cataclean.

Yeah, I've been running CRC Guaranteed to Pass at the moment, but haven't seen any changes in the differential readings from the two bank's O2 sensors. I do have Cataclean on hand. That's perhaps my last ditch effort, and I plan to use it after I run the gas tank down a little bit more.


Any other thoughts?

[E92_William]

If nothing works have him put an o2 sensor spacer down there and get the damn thing to pass and you can sort it out later

[PhaseP]

Originally Posted by gopomyaw

>Any other thoughts?

Depending on state laws, you may pass inspection with 1 or 2 "not ready".

[John 070]

Originally Posted by PhaseP

Depending on state laws, you may pass inspection with 1 or 2 "not ready".

I've heard even Calif. allows that (1 not ready).

This is clearly the case in PA per the code. Yet, garages told me "NO!"

They're the keeper of the stickers, what sense does it make to argue? They told me no big deal, just keep driving and come in when ready. For my wife's GM? If the battery is disconnected it is almost 800 miles before the I/M shows ready (namely EVAP). I tried the drive cycle to no avail, and the garage told me they have done the same which is why they say just drive. So we drove uninspected for a month and the month changed on the sticker.

What I would be curious is if OP's scenario is due to a real problem, or this is typical of BMW, since it is typical of GM (not Lexus and Nissan those come back in 70-80 miles of normal driving)....

[RayLivingston]

P2096 is not the code I would expect to see for a failed cat. There are specific codes for cat efficiency that I would expect to see first.

Is it passing all O2 sensor monitors? P2096 could indicate a failed sensor, particularly a post-cat sensor. But P2096 indicates the ECU is seeing lean mixture on the post-cat sensor, but your 0.8V reading indicates it is rich. That does not make sense. What do the pre-cat sensors show on a warm engine? They should be constantly cycling between ~0.1V and ~0.9V, give or take.

[gopomyaw]

If nothing works have him put an o2 sensor spacer down there and get the damn thing to pass and you can sort it out later

Great, idea but I'm unsure if this will fully solve the problem. Bank 1's pre-cat sensor is also consistently showing rich (lambda <1.0)...it's like 0.96-0.98. Bank 2's pre-cat is pretty steady at 1.0. I'm guessing the DME doesn't like this when running the monitor because it appears as though I have the foot on the gas (even though I don't).

I guess I could try but I'm running out of time on my sticker.

I've heard even Calif. allows that (1 not ready).

Sadly, I don't think the 1 that is unready can be the Catalyst Monitor. See:
https://www.smogtips.com/smog-questi...itor-Not-Ready
"For all 2000 and newer gasoline powered vehicles, one monitor is still allowed incomplete however this must must be the EVAP monitor. All other monitors have to be ready or completed."

And I've seen this same info elsewhere. It makes sense because Catalyst monitoring is a key part of smog testing!

Is it passing all O2 sensor monitors? P2096 could indicate a failed sensor, particularly a post-cat sensor. But P2096 indicates the ECU is seeing lean mixture on the post-cat sensor, but your 0.8V reading indicates it is rich. That does not make sense. What do the pre-cat sensors show on a warm engine? They should be constantly cycling between ~0.1V and ~0.9V, give or take.

BINGO! You have hit the nail on the head and why this is so confusing.

To answer your question, the pre-cat sensors are "current based" and showing the lambda value (i.e., 0.95 to 1.05 during normal driving) instead of a voltage. But they also show similar discrepancies as the post-cat -- that is, pre-cat Bank 1 is rich (0.96-0.98) when pre-cat Bank 2 is pretty consistently nominal at 1.0.

When driving I do see variation in both pre-cat and post-cat.

O2 Sensors tests pass. They were replaced just a month ago as part of this fishing expedition.

Here's my theory:
- P2096 was thrown sometime way in the past...hard to know when. Could have been as my cat was transitioning from okay-ish to not-so-okay-ish.

- We sadly have no good history on that event due to the nature DTCs. No timestamp, no measurement data, etc.

- Now that I've cleared the code, I consistently see the fuel is rich, both pre-cat and post-cat.

- No other red flags...no misfires and everything else is nominal. No other codes being thrown.

- Drive cycle on Bank 2 consistently completes. In fact, check out these past stats:

$21 - Catalyst Monitor Bank 1 TID $81 - Manufacturer Defined 0 0 0 [INCOMPLETE]
$22 - Catalyst Monitor Bank 2 TID $81 - Manufacturer Defined 0.1093 0 0.9218 Pass

0x02 Catalyst Monitor Completion Counts Bank 1 2903
0x03 Catalyst Monitor Conditions Encountered Counts Bank 1 2174
0x04 Catalyst Monitor Completion Counts Bank 2 3670
0x05 Catalyst Monitor Conditions Encountered Counts Bank 2 2293

There are far more completions on Bank 2, and that can't just be from the last month of driving. So this condition has been going on unnoticed for quite a while. (Unsure why conditions encountered is less than completions count...but let's ignore that for a sec.) When I drive, I see conditions encountered counts uptick on both banks, but only completion count uptick on Bank 2. Bank 1 completion count has been stuck at 2903 ever since I have been monitoring this.

- Cat is likely clogged...resulting in rich mixture coming out the back and also backpressure creating rich readings in front.

- Note that the car otherwise drives great.

Would love to hear if there are any other thoughts.

Thanks,
-G

p.s. BTW, for folks who are interested, check out this really informative explanation of the O2 sensors: https://bimmerprofs.com/management-lambda-probes/. I took me a couple of passes to get through some of the grammar and phrasing, but I think there's some good info in there for anyone who is dealing with this part of the system.

[lookalikehuuh]

Originally Posted by E92_William

If nothing works have him put an o2 sensor spacer down there and get the damn thing to pass and you can sort it out later

Try this, I have used it a couple of times on my old IS300 and my mom's Tundra that both had P0420 codes for efficiency codes.