2C31 code

MathewM4 · 03-12-2020, 07:05 PM

2011 BMW 328i with 2C31 code.

I recently replaced both pre cat O2 sensors with Bosch 11787558055 and 11787558073 after fault code 2C2B. The O2 sensors were installed correctly.

Does anyone have a suggestion to the 2C31 code?

This car is starting to get on my nerves!!

dpaul · 03-12-2020, 09:06 PM

Assuming your new sensor is not faulty, the next thing I'd look for would be a small exhaust leak. Mostly likely a gasket but also possibly an improperly tightened O2 sensor. Smoke or pressure test is pretty easy.

MathewM4 · 03-12-2020, 11:19 PM

The car just through a second code, 2CB6, O2 sensor after cat conv.: Signal fixed lean.

post cat O2 sensor bank 1 or 2 stuck lean?

gbalthrop · 03-13-2020, 12:59 AM

Quote:

Originally Posted by MathewM3

2011 BMW 328i with 2C31 code. I recently replaced both pre cat O2 sensors with Bosch 11787558055 and 11787558073 after fault code 2C2B. The O2 sensors were installed correctly. [Were the Connectors Reversed, Bank 1 vs. Bank 2? INPA has a test for that.

]

Quote:

Originally Posted by MathewM3

The car just through a second code, 2CB6, O2 sensor after cat conv.: Signal fixed lean...

Here are the BMW Fault Code Lookup Definitions for the two codes, with Fault Information Sheet Link for each. First suspect is that the connectors are reversed, meaning Bank 1 Pre-cat sensor is plugged into Bank 2 chassis connector, and vice-versa:
N52 | P2096 | 2C31 | DME: Oxygen sensor control | MSV80
http://www.bmwfault.codes/XMLDiagVie...cANQA5ADAANAA=

2CB6 | DME: Oxygen sensor after catalytic converter: Signal fixed at lean | msd80
http://www.bmwfault.codes/XMLDiagVie...MAOQAxADAANAA=

George

dpaul · 03-13-2020, 05:45 AM

I'd suspect that as well except:

1) the OP replaced the pre-cat sensors because he first observed a 2C2B code
2) the OP made a point of stating that the new sensors were installed correctly.
3) All codes are bank 1 - if there was a connector swap on the pre-cats there'd likely be codes on both banks.

MathewM4 · 03-13-2020, 10:36 AM

The connectors have not been reversed by me for sure. The previous owner could have reversed them but I have driven +30K miles since purchase.

Wouldn't the fault codes showed up much earlier if the previous owner reversed the connectors?

dpaul · 03-14-2020, 05:09 AM

Quote:

Originally Posted by MathewM3

The connectors have not been reversed by me for sure. The previous owner could have reversed them but I have driven +30K miles since purchase.

Wouldn't the fault codes showed up much earlier if the previous owner reversed the connectors?

Yes, they would have

03-12-2020, 07:05 PM	#1
MathewM4 Private First Class 70 Rep 145 Posts Drives: BMW M4 and BMW M3 E46 Join Date: Jun 2014 Location: Dallas Texas iTrader: (0) Garage List 2016 BMW M4 [0.00] 2002 BMW M3 [0.00]	2C31 code 2011 BMW 328i with 2C31 code. I recently replaced both pre cat O2 sensors with Bosch 11787558055 and 11787558073 after fault code 2C2B. The O2 sensors were installed correctly. Does anyone have a suggestion to the 2C31 code? This car is starting to get on my nerves!!
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03-12-2020, 09:06 PM	#2
dpaul Lieutenant Colonel 654 Rep 1,893 Posts Drives: 2009 E90 335xi, 2011 E93 M3 Join Date: Dec 2012 Location: Boston iTrader: (3)	Assuming your new sensor is not faulty, the next thing I'd look for would be a small exhaust leak. Mostly likely a gasket but also possibly an improperly tightened O2 sensor. Smoke or pressure test is pretty easy.
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03-12-2020, 11:19 PM	#3
MathewM4 Private First Class 70 Rep 145 Posts Drives: BMW M4 and BMW M3 E46 Join Date: Jun 2014 Location: Dallas Texas iTrader: (0) Garage List 2016 BMW M4 [0.00] 2002 BMW M3 [0.00]	The car just through a second code, 2CB6, O2 sensor after cat conv.: Signal fixed lean. post cat O2 sensor bank 1 or 2 stuck lean?
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03-13-2020, 05:45 AM	#5
dpaul Lieutenant Colonel 654 Rep 1,893 Posts Drives: 2009 E90 335xi, 2011 E93 M3 Join Date: Dec 2012 Location: Boston iTrader: (3)	I'd suspect that as well except: 1) the OP replaced the pre-cat sensors because he first observed a 2C2B code 2) the OP made a point of stating that the new sensors were installed correctly. 3) All codes are bank 1 - if there was a connector swap on the pre-cats there'd likely be codes on both banks.
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03-13-2020, 10:36 AM	#6
MathewM4 Private First Class 70 Rep 145 Posts Drives: BMW M4 and BMW M3 E46 Join Date: Jun 2014 Location: Dallas Texas iTrader: (0) Garage List 2016 BMW M4 [0.00] 2002 BMW M3 [0.00]	The connectors have not been reversed by me for sure. The previous owner could have reversed them but I have driven +30K miles since purchase. Wouldn't the fault codes showed up much earlier if the previous owner reversed the connectors?
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