o2 Sensor Codes

pysical

Sergeant
Jun 16, 2017
471
108
0
Ride
2009 335xi E90
I get these randomly if I go WOT. Causes the car to run like crap until I stop and clear it out.

2C3D - DME: Oxygen sensor before catalytic converter: Line fault.
2C3E - DME: Oxygen sensor 2 before catalytic converter: Line fault.
2C7B - DME: Oxygen sensor after catalytic converter: Signal.
2C7C - DME: Oxygen sensor 2 after catalytic converter: Signal.
2CAA - DME: Oxygen sensor before catalytic converter: Temperature.
2CAB - DME: Oxygen sensor 2 before catalytic converter: Temperature.


Anyone know what the issue could be? They are all new 6 month old o2 sensors. I thought about testing with INPA but I don't know what I would be looking for.
 

veer90

Lieutenant
Nov 16, 2016
1,000
774
0
West Nyack, NY
Ride
e90 335i 6MT
Inspect the wiring harnesses for both pre-cat O2s. If the wiring checks out then the sensors are done.

I'd guess you left the wires too close to the manifolds and it burned up the insulation. Happened to me once
 

pysical

Sergeant
Jun 16, 2017
471
108
0
Ride
2009 335xi E90
Inspect the wiring harnesses for both pre-cat O2s. If the wiring checks out then the sensors are done.

I'd guess you left the wires too close to the manifolds and it burned up the insulation. Happened to me once

The wires are far from the manifold. But I did get new ones that will be here tomorrow.

Logged a mini pull. The Motiv ECA jacked up and said 4.95v constant and 49.8%. And STFTs were 34%+.

Then did one on the way home and ECA was working correctly and STFTs went to -34%...

Hopefully the new o2 sensors fix this.
 

BreakMyBillfold

Specialist
Nov 18, 2016
81
34
0
AZ
You're replacing both precat and postcat sensors? I did my precats ones thinking the postcats ones were only for checking cat presence and not for tuning, but my mixture 2 codes persisted until I replaced the postcat one too.
 

pysical

Sergeant
Jun 16, 2017
471
108
0
Ride
2009 335xi E90
You're replacing both precat and postcat sensors? I did my precats ones thinking the postcats ones were only for checking cat presence and not for tuning, but my mixture 2 codes persisted until I replaced the postcat one too.

My o2 sensors are warranted. If these pre cost sensors do nothing then I will do the post cat ones. I also have some used ones I can try to see if anything changes.
 
May 15, 2018
20
6
0
Ride
08 335xi E92
My o2 sensors are warranted. If these pre cost sensors do nothing then I will do the post cat ones. I also have some used ones I can try to see if anything changes.
Which o2 sensors ended up being the ones causing the signal codes? I am having a very similar issue.
 

boosted.n54

Lurker
Oct 28, 2019
17
1
0
Ride
2008 BMW 335xi
I am also throwing 2c78 post cat bank 2 o2 sensor code consistently even though I have replaced all of my oxygen sensors. It comes on immediately after just a couple of minutes of driving and it has me stumped on what is causing this code to pop up.

Here is a datalog: https://datazap.me/u/rnmevo9/2nd-revision-e45?log=0&data=3-20
Do You have catless downpipes and custom tune by chance ? What mods and setup you have.
 

RNM

Corporal
Jun 3, 2019
175
166
0
Do You have catless downpipes and custom tune by chance ? What mods and setup you have.

Yes to both questions. Here is a list of modifications:

RB GF 17t turbos
RB external pcv valve
RB outlets
Mhd custom tuned by BQ on e45
BMS stock location inlets
Vrsf downpipes and street exhaust
Vrsf charge pipe with raceport bov
Psp 900 intercooler
Psp external oil cooler
Relocated 335d coolant tank
Fuel it stage 2 lpfp 525 pump
EOSpeed bpm4 lpfp controller
Index 12 injectors
Precision raceworks fuel filter assembly
Spool hpfp overdrive
 
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boosted.n54

Lurker
Oct 28, 2019
17
1
0
Ride
2008 BMW 335xi
I recently did a engine swap on my 335 with bottom mount single turbo setup, I also am running a custom MHD tune using the Motiv Reflex unit to control port injection and boost control. I am getting these codes that pop up once I drive for 10 minutes or so 2c3d oxygen sensor before catalytic converter. Line fault 2c3e Oxygen sensor 2 before catalytic converter. Line fault. I believe the car goes into closed loop where the AFRs go from 12-13 jump to 26 and get stuck and my STFT gets stuck at zero. It's always these same two codes I get every time. Sometimes I do get a SES light that pops up. I did switch to single bank o2 fueling and double checked the position of the o2 sensors and wire routing making sure nothing gets melted and it is correct. Yes I do have the box checked for single bank fueling option. The primary o2 sensor is brand new Bosch if anybody was wondering. I was thinking of doing a smoke test this weekend to see if I find any vacuum leaks possibly? Any kind of insight or help would be very much appreciated.
 

boosted.n54

Lurker
Oct 28, 2019
17
1
0
Ride
2008 BMW 335xi
Yes to both questions. Here is a list of modifications:

RB GF 17t turbos
RB external pcv valve
RB outlets
Mhd custom tuned by BQ on e45
BMS stock location inlets
Vrsf downpipes and street exhaust
Vrsf charge pipe with raceport bov
Psp 900 intercooler
Psp external oil cooler
Relocated 335d coolant tank
Fuel it stage 2 lpfp 525 pump
EOSpeed bpm4 lpfp controller
Index 12 injectors
Precision raceworks fuel filter assembly
Spool hpfp overdrive
Did you ever figure out a resolution to the o2 codes?