What does this code mean and why does it keep reappearing?

N54Society · 02-15-2016, 02:02 PM

2C7B Lambda probe behind catalytic converter, signal

I just started getting it recently. I've done a couple of code resets but it keeps coming back so I'm thinking it might be an actual issue.

I have not touched my O2 sensors since my downpipes were installed which was a long time ago. I've verified that they're installed correctly so it's not that. Anyone have an idea what it could be?

TBN54 · 02-15-2016, 02:03 PM

Oxygen Sensor.

N54Society · 02-15-2016, 02:08 PM

Quote:

Originally Posted by TBN54

Oxygen Sensor.

How would I be able to identify exactly which one it is in order to replace it?

TBN54 · 02-15-2016, 02:09 PM

Well it wouldn't.

That part is up to you or the person doing the job. Just have to pull both and see for yourself.

jwalker87 · 02-15-2016, 02:26 PM

First result when googling "2C7B BMW": http://www.e90post.com/forums/showthread.php?t=564145

"2C7B After cat o2 Sensor signal, Bank 1"

I can't remember which one Bank 1 is, but that's what 2C7B is.

N54Society · 02-15-2016, 03:18 PM

Quote:

Originally Posted by jwalker87

First result when googling "2C7B BMW": http://www.e90post.com/forums/showthread.php?t=564145

"2C7B After cat o2 Sensor signal, Bank 1"

I can't remember which one Bank 1 is, but that's what 2C7B is.

Thanks! Trying to figure out which one of these two I need now:

jwalker87 · 02-15-2016, 04:06 PM

In case you check this forum before n54tech: the one with o2 sensor #04.

limitdown · 02-15-2016, 09:08 PM

I concur with jwalker. #1 and #4 sensors are for bank 1.
These don't break as often as precat sensors. With precat codes, they might be caused by injectors, plugs, coils, LPFP, HPFP.
With postcat codes, it's usually the sensor itself

Stroker1 · 02-16-2016, 06:51 AM

Oem color.coding is black lead bank1, gray lead.bank 2.

Jklad · 02-16-2016, 09:32 AM

Honestly, if you are over 60k miles and are going to replace the one side sensor you should just replace both banks and be done with it.

loknar · 02-16-2016, 09:35 AM

Does this trigger a check engine light? if not maybe just ignore it?

N54Society · 02-16-2016, 08:52 PM

Quote:

Originally Posted by Stroker1

Oem color.coding is black lead bank1, gray lead.bank 2.

That's really helpful, thanks.

Quote:

Originally Posted by Jklad

Honestly, if you are over 60k miles and are going to replace the one side sensor you should just replace both banks and be done with it.

It's not too hard to get under my car with ramps. I'll hold off until the other goes bad.

Quote:

Originally Posted by loknar

Does this trigger a check engine light? if not maybe just ignore it?

Yes it does. A little tip from Steve at Fuel-it:

Quote:

Always order the 560mm one...then it can be used on either bank for replacement or troubleshooting.

Luckystrike24 · 02-16-2016, 09:24 PM

Quote:

Always order the 560mm one...then it can be used on either bank for replacement or troubleshooting.

No you can't the plugs are keyed differently even though the shape is the same.

The pre cat o2 sensors can be used on either bank though

ferocity02 · 02-17-2016, 12:40 AM

I'm getting the same code and my rear O2 sensors are new. Also getting the aging code for the same sensor. No fix yet.

I've heard it can be related to a poor connection at the DME. Have you recently done any work on or near the DME? I haven't so that's not my issue I don't think.

N54Society · 02-17-2016, 05:35 AM

Quote:

Originally Posted by Luckystrike24

No you can't the plugs are keyed differently even though the shape is the same.

The pre cat o2 sensors can be used on either bank though

Maybe he was thinking of the precat ones? Weird, he usually knows his stuff.

Quote:

Originally Posted by ferocity02

I'm getting the same code and my rear O2 sensors are new. Also getting the aging code for the same sensor. No fix yet.

I've heard it can be related to a poor connection at the DME. Have you recently done any work on or near the DME? I haven't so that's not my issue I don't think.

I recently removed my JB4 (went full flash tune) and installed the dp fix momentarily and then removed that as well after passing smog. There was a lot of time between the dp fix install/uninstall and this code though so I think mine is legitimately bad.

AWSAWS · 02-17-2016, 06:17 AM

Quote:

Originally Posted by vbp6us

Maybe he was thinking of the precat ones? Weird, he usually knows his stuff.

I recently removed my JB4 (went full flash tune) and installed the dp fix momentarily and then removed that as well after passing smog. There was a lot of time between the dp fix install/uninstall and this code though so I think mine is legitimately bad.

Reset adaptations first if u haven't already. See if it returns after clearing the codes.

N54Society · 02-17-2016, 03:03 PM

Quote:

Originally Posted by AWSAWS

Reset adaptations first if u haven't already. See if it returns after clearing the codes.

Which ones specifically? Thanks

Miller335 · 02-17-2016, 10:35 PM

Quote:

Originally Posted by vbp6us

Which ones specifically? Thanks

I'm guessing the A/F mixtures.

limitdown · 02-18-2016, 01:15 AM

Also try reseting lambda adaptations. Hopefully it works for you.

N54Society · 02-18-2016, 02:51 AM

Quote:

Originally Posted by Miller335

I'm guessing the A/F mixtures.

Quote:

Originally Posted by limitdown

Also try reseting lambda adaptations. Hopefully it works for you.

I reset both along with octane (went to E85 map) and so far it hasn't returned. I may need to drive some more though.

N54Society · 03-09-2016, 04:44 PM

It came back. My new one also arrived so I'll be installing that today.

fmonteiro444 · 03-09-2016, 05:02 PM

Quote:

Originally Posted by vbp6us

It came back. My new one also arrived so I'll be installing that today.

Do your fuel trims deviate bank to bank?

02-15-2016, 02:02 PM	#1
N54Society Major Private First Class 449 Rep 1,327 Posts Drives: 2010 E90 335i M Sport Join Date: Mar 2014 Location: US, NA, Earth, Milky Way Galaxy iTrader: (2)	What does this code mean and why does it keep reappearing? 2C7B Lambda probe behind catalytic converter, signal I just started getting it recently. I've done a couple of code resets but it keeps coming back so I'm thinking it might be an actual issue. I have not touched my O2 sensors since my downpipes were installed which was a long time ago. I've verified that they're installed correctly so it's not that. Anyone have an idea what it could be? __________________ 2008 E92 335i 6MT: FBO + MMP Silicone Inlets \| Stage 1 LPFP \| 335is clutch + MFactory SMFW \| Custom BuraQ + MHD tune \| 3.5Bar N20 sensor [SOLD] 2010 E90 335i M-Sport AT: 5" Stepped FMIC, Stage 2 LPFP - MHD V7 E60 Tune running 100% E85 - VRSF DPs
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02-15-2016, 02:03 PM	#2
TBN54 Captain 427 Rep 793 Posts Drives: 08' E92 335 -> 17' F30 340i Join Date: Dec 2015 Location: Upstate NY iTrader: (0)	Oxygen Sensor.
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02-15-2016, 02:26 PM	#5
jwalker87 Major 318 Rep 1,021 Posts Drives: '08 335i, '11 335xi, '01 Z3M Join Date: Jul 2010 Location: Pittsburgh, PA iTrader: (2)	First result when googling "2C7B BMW": http://www.e90post.com/forums/showthread.php?t=564145 "2C7B After cat o2 Sensor signal, Bank 1" I can't remember which one Bank 1 is, but that's what 2C7B is. __________________ 2001 e36/7 M Roadster 5spd 2008 e90 335i 6spd 2011 e90 335xi 6spd 2011 e70 x5 diesel 2010 Ducati Monster 696
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02-15-2016, 04:06 PM	#7
jwalker87 Major 318 Rep 1,021 Posts Drives: '08 335i, '11 335xi, '01 Z3M Join Date: Jul 2010 Location: Pittsburgh, PA iTrader: (2)	In case you check this forum before n54tech: the one with o2 sensor #04. __________________ 2001 e36/7 M Roadster 5spd 2008 e90 335i 6spd 2011 e90 335xi 6spd 2011 e70 x5 diesel 2010 Ducati Monster 696
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02-15-2016, 09:08 PM	#8
limitdown First Lieutenant 187 Rep 337 Posts Drives: 2007 335i E93 Join Date: Jul 2015 Location: Location iTrader: (0)	I concur with jwalker. #1 and #4 sensors are for bank 1. These don't break as often as precat sensors. With precat codes, they might be caused by injectors, plugs, coils, LPFP, HPFP. With postcat codes, it's usually the sensor itself
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02-15-2016, 02:09 PM	#4
TBN54 Captain 427 Rep 793 Posts Drives: 08' E92 335 -> 17' F30 340i Join Date: Dec 2015 Location: Upstate NY iTrader: (0)	Well it wouldn't. That part is up to you or the person doing the job. Just have to pull both and see for yourself.
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02-16-2016, 06:51 AM	#9
Stroker1 Private 35 Rep 91 Posts Drives: 07 335 cp dci, ***dp's, jb4 Join Date: Sep 2015 Location: atlanta ga iTrader: (0)	Oem color.coding is black lead bank1, gray lead.bank 2.
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02-16-2016, 09:32 AM	#10
Jklad Lieutenant Colonel 421 Rep 1,643 Posts Drives: 2007 335i Coupe Join Date: Nov 2010 Location: Palatine, IL iTrader: (0)	Honestly, if you are over 60k miles and are going to replace the one side sensor you should just replace both banks and be done with it. __________________ 2007 E92 335i MT
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02-16-2016, 09:35 AM	#11
loknar Private First Class 46 Rep 167 Posts Drives: 335i e90 iDrive Join Date: Jan 2016 Location: Canada iTrader: (0)	Does this trigger a check engine light? if not maybe just ignore it?
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02-17-2016, 12:40 AM	#14
ferocity02 Colonel 530 Rep 2,083 Posts Drives: 2013 135is Join Date: May 2014 Location: USA iTrader: (8)	I'm getting the same code and my rear O2 sensors are new. Also getting the aging code for the same sensor. No fix yet. I've heard it can be related to a poor connection at the DME. Have you recently done any work on or near the DME? I haven't so that's not my issue I don't think.
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02-18-2016, 01:15 AM	#19
limitdown First Lieutenant 187 Rep 337 Posts Drives: 2007 335i E93 Join Date: Jul 2015 Location: Location iTrader: (0)	Also try reseting lambda adaptations. Hopefully it works for you.
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03-09-2016, 04:44 PM	#21
N54Society Major Private First Class 449 Rep 1,327 Posts Drives: 2010 E90 335i M Sport Join Date: Mar 2014 Location: US, NA, Earth, Milky Way Galaxy iTrader: (2)	It came back. My new one also arrived so I'll be installing that today. __________________ 2008 E92 335i 6MT: FBO + MMP Silicone Inlets \| Stage 1 LPFP \| 335is clutch + MFactory SMFW \| Custom BuraQ + MHD tune \| 3.5Bar N20 sensor [SOLD] 2010 E90 335i M-Sport AT: 5" Stepped FMIC, Stage 2 LPFP - MHD V7 E60 Tune running 100% E85 - VRSF DPs
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