[Strandh]

Hello,
Would be very thankful if anyone with experience or knowledge on how to go forward with below:

I mounted the original catalytic converter back for inspection, usually runs catless. On the way to the inspection I got engine lamp on and following fault code: 12AD01 - Oxygen sensor after catalytic converter: signal fixed at lean.

I erased the fault code, engine lamp disappeared.
But I failed the inspection due to Lambda (AFR) and unburnt fuel in the exhaust.

On the way back home I monitored the lambda value and it jumped back and forth all the way from like 0,85-1,12. And I got the following fault codes.
Active:
128301 - Oxygen sensor before catalytic converter, system check: signal fixed at rich
12AD01 - Oxygen sensor after catalytic converter: signal fixed at lean
Inactive:
12BD80 - Oxygen sensor before catalytic converter: Multiple fault

Since the car had been parked for 1,5 year I tested to fuel it up with fresh, good octane fuel also added some E85. after that I got a much more stable lambda around 0,98-1,02 during driving in stable highway speed.

I went on inspection again, failed on lambda and un-burnt fuel in the exhaust.
He was really nice and suggested that I would drive the shit of the car for a while and come back. I did, the brakes smelled when I came back
And the vehicle passed this time with very good values.

On the way from the inspection I once again got MIL lamp with fault code: 12AD01 - Oxygen sensor after catalytic converter: signal fixed at lean.

What is the first to fault trace?
Can it be leak from Turbo to Cat that makes this behvior?
I just want to go back to catless and tune the vehicle again
Btw, N55, running Dorch stage 1, MHD Software with flex fuel HW installed, Have WMI installed but only inject water to get better cooling when driving on hot track days, Wagner intercooler, one step colder plugs gapped 0,55mm, high flow air filter in stock box.

Big thanks,
Simon

[EnzoKhan]

Originally Posted by Strandh

Hello,
Would be very thankful if anyone with experience or knowledge on how to go forward with below:

I mounted the original catalytic converter back for inspection, usually runs catless. On the way to the inspection I got engine lamp on and following fault code: 12AD01 - Oxygen sensor after catalytic converter: signal fixed at lean.

I erased the fault code, engine lamp disappeared.
But I failed the inspection due to Lambda (AFR) and unburnt fuel in the exhaust.

On the way back home I monitored the lambda value and it jumped back and forth all the way from like 0,85-1,12. And I got the following fault codes.
Active:
128301 - Oxygen sensor before catalytic converter, system check: signal fixed at rich
12AD01 - Oxygen sensor after catalytic converter: signal fixed at lean
Inactive:
12BD80 - Oxygen sensor before catalytic converter: Multiple fault

Since the car had been parked for 1,5 year I tested to fuel it up with fresh, good octane fuel also added some E85. after that I got a much more stable lambda around 0,98-1,02 during driving in stable highway speed.

I went on inspection again, failed on lambda and un-burnt fuel in the exhaust.
He was really nice and suggested that I would drive the shit of the car for a while and come back. I did, the brakes smelled when I came back
And the vehicle passed this time with very good values.

On the way from the inspection I once again got MIL lamp with fault code: 12AD01 - Oxygen sensor after catalytic converter: signal fixed at lean.

What is the first to fault trace?
Can it be leak from Turbo to Cat that makes this behvior?
I just want to go back to catless and tune the vehicle again
Btw, N55, running Dorch stage 1, MHD Software with flex fuel HW installed, Have WMI installed but only inject water to get better cooling when driving on hot track days, Wagner intercooler, one step colder plugs gapped 0,55mm, high flow air filter in stock box.

Big thanks,
Simon

Were you able to find a solution? I am having a similar problem:

I was getting 2BCB (mixture control: exhaust gas after catalytic converter too lean) code along with 2D2F (oxygen sensor before cat: multiple fault). 2cF4 code showed up once but didnt return after clearing (before cat slow response). This prompted me to replace the primary O2 sensor.

After replacing the primary O2 sensor and driving for a bit these two codes came up:
2D34 ( oxygen sensor before catalytic converter, system check: signal fixed at rich.
2D2F (Oxygen sensor before cat multiple fault)

The car drives and pulls smooth. It idles smooth as well before and after replacing the sensor. No SES light illuminated yet. What can I do now to hopefully resolve this matter and ensure the engine isnt running too rich or lean?

Car info:

2011 e92, N55 with 126k miles. Catless downpipe with mhd stage 0 tune for the past year. Just regular oil changes. No other work was done recently.

If you can please shed some light on this matter, that'd be greatly appreciated, thank you!