[m_star01]

My E90, 2010, 320i failed MOT due to:

"exhaust lambda reading after 2nd fast idle outside specified limits (8.2.1.2 (c))"

Was told by garage i need new oxygen sensors. I wanted to ask and get a second opinion if that diagnosis is correct? I purchased a code reader and attached is the codes i got.

The car drives and no EML so i am really confused about the above errors not sure where to do, anyone advise if this is a simple case to replace the o2 sensors or something else?

[m_star01]

anyone help?

[gbalthrop]

Originally Posted by m_star01

My E90, 2010, 320i failed MOT due to:
"exhaust lambda reading after 2nd fast idle outside specified limits (8.2.1.2 (c))"
Was told by garage [NOT a BMW specialist $hop, I presume?] i need new oxygen sensors. [WHICH ones, and what other tests did they conduct, w/results?] I wanted to ask and get a second opinion if that diagnosis is correct? I purchased a code reader and attached is the codes i got. The car drives and no EML so i am really confused about the above errors not sure where to do, anyone advise if this is a simple case to replace the o2 sensors or something else?

Replacing parts is relatively simple. DIAGNOSIS of what is CAUSING a fault, and what needs to be repaired (WHO does that anymore? ;-) or replaced is the "Lost Art", as it takes TIME & THOUGHT. Sensors are intended to DETECT "Out of Range" issues. When they do, that does NOT mean replace the sensor. If you CAREFULLY read & analyze the Fault Information Sheets linked below, you will SEE that the "garage" skipped a few steps in TESTING/ DIAGNOSIS.

The PRIMARY Fault is 2C7F(trim control), and the "Secondary" Fault is 2C6C (System Check). BOTH of those Faults relate to "Bank 2" or 2nd/Rearmost Exhaust Manifold. The Fault Code Definitions on your Ancel BM500 agree with those found in BMW Fault Code Lookup:
https://bmwfault.codes/

Here are the Links to Fault Info Sheets for those two codes:
https://bmwfault.codes/XMLDiagView?d...AANQA5ADAANAA=
https://bmwfault.codes/XMLDiagView?d...cAOAAyADAANAA=

As you can see from the "Service Notes" at bottom of each Sheet, the FIRST step is to check/test to see if the O2 Sensor Connectors are REVERSED, or connector plugged into WRONG sensor. WHEN did SOMEONE last do anything under the Bonnet & WHAT was done? Next step is to Inspect/ Test Wiring for O2 Sensors on Bank 2. $hops are usually good at replacing parts, and taking your money. DIAGNOSIS: NOT so much.

I don't know anything about the Ancel BM500 except the Manual (available online) indicates it can display Live Data ("Read Datastream"). If it can display Fuel Trims (Short Term), you can quickly tell if O2 Sensor connectors are reversed. That Datastream/ Live Data will also allow you to compare values shown for Bank 1 & Bank 2. You have faults for Bank 2 but NOT Bank 1.

YOU can probably find the issue YOURSELF, at NO expense, using your Ancel BM500 and a Multimeter (Cheapest available @ Amazon UK if you don't have one), and Forum Help. Please post back for details, and when you do, please indicate:
1) Last-7 Characters of your VIN;
2) Engine designation: N43 or N46?

We can provide ISTA ScreenPrints showing Location of Connectors, Connector View (Pin designations), wiring diagrams with wiring colors, and specific test suggestions.
George

[m_star01]

Sure i will get the car and do a live data stream. Should i clear faults and drive it then put on the Ancel and i will compare values for the 2 sensors after the cat. i will let you know the values as i have a feeling 1 of the 2 maybe not in sync with the other o2 sensor.

[gbalthrop]

Originally Posted by m_star01

Sure i will get the car and do a live data stream. Should i clear faults and drive it then put on the Ancel and i will compare values for the 2 sensors after the cat. i will let you know the values as i have a feeling 1 of the 2 maybe not in sync with the other o2 sensor.

I'm NOT a Lambda Sensor Guru, as I have never had an O2 Sensor issue. However, my interpretation of the code Definitions & Fault Info Sheets is that the PRE-Cat O2 Sensors, responsible for "Trim" of enrichment, have reversed connectors, OR there is an issue with the Signal from the Bank 2 Pre-cat sensor ALWAYS showing LEAN ("Stuck on Lean").

If that interpretation is CORRECT, then I would expect to see a large difference in STFT between Bank 1 & Bank 2 Pre-cat Sensor signals, or if your Ancel can display actual Lambda Sensor Voltage Signal, a difference in THOSE Voltage values. It COULD be intermittent, or it COULD be constant.
George

[Tambohamilton]

I'm better with spanners than I am with electrics, so I'd start by throwing a new lambda sensor at it (whichever one it specifies in the codes).

[gbalthrop]

Originally Posted by Tambohamilton

I'm better with spanners than I am with electrics, so I'd start by throwing a new lambda sensor at it (whichever one it specifies in the codes).

Did you open the links to the Fault Information Sheets and READ the Service Notes?
George

[Tambohamilton]

Originally Posted by gbalthrop

Did you open the links to the Fault Information Sheets and READ the Service Notes?
George

Hell no! Now where's my parts cannon...?

[Suvorovo]

Originally Posted by Tambohamilton

Hell no! Now where's my parts cannon...?

Can I send you some part numbers for my car?

[Serf27]

Originally Posted by gbalthrop

Replacing parts is relatively simple. DIAGNOSIS of what is CAUSING a fault, and what needs to be repaired (WHO does that anymore? ;-) or replaced is the "Lost Art", as it takes TIME & THOUGHT. Sensors are intended to DETECT "Out of Range" issues. When they do, that does NOT mean replace the sensor. If you CAREFULLY read & analyze the Fault Information Sheets linked below, you will SEE that the "garage" skipped a few steps in TESTING/ DIAGNOSIS.

The PRIMARY Fault is 2C7F(trim control), and the "Secondary" Fault is 2C6C (System Check). BOTH of those Faults relate to "Bank 2" or 2nd/Rearmost Exhaust Manifold. The Fault Code Definitions on your Ancel BM500 agree with those found in BMW Fault Code Lookup:
https://bmwfault.codes/

Here are the Links to Fault Info Sheets for those two codes:
https://bmwfault.codes/XMLDiagView?d...AANQA5ADAANAA=
https://bmwfault.codes/XMLDiagView?d...cAOAAyADAANAA=

As you can see from the "Service Notes" at bottom of each Sheet, the FIRST step is to check/test to see if the O2 Sensor Connectors are REVERSED, or connector plugged into WRONG sensor. WHEN did SOMEONE last do anything under the Bonnet & WHAT was done? Next step is to Inspect/ Test Wiring for O2 Sensors on Bank 2. $hops are usually good at replacing parts, and taking your money. DIAGNOSIS: NOT so much.

I don't know anything about the Ancel BM500 except the Manual (available online) indicates it can display Live Data ("Read Datastream"). If it can display Fuel Trims (Short Term), you can quickly tell if O2 Sensor connectors are reversed. That Datastream/ Live Data will also allow you to compare values shown for Bank 1 & Bank 2. You have faults for Bank 2 but NOT Bank 1.

YOU can probably find the issue YOURSELF, at NO expense, using your Ancel BM500 and a Multimeter (Cheapest available @ Amazon UK if you don't have one), and Forum Help. Please post back for details, and when you do, please indicate:
1) Last-7 Characters of your VIN;
2) Engine designation: N43 or N46?

We can provide ISTA ScreenPrints showing Location of Connectors, Connector View (Pin designations), wiring diagrams with wiring colors, and specific test suggestions.
George

If the plugs were switched, wouldn’t there be codes for both bank 1 and 2?
The links says “1. Initiate system test for reversed O2 sensors. Follow instructions for system test.”
Am I missing something or how is that test initiated?

[m_star01]

Still confused how the sensors be reversed is that a term or you actually mean someone swapped them around?

[Tambohamilton]

They could actually be plugged into the wrong connectors - physically switched around

[Tambohamilton]

Originally Posted by Suvorovo

Can I send you some part numbers for my car?

If I can send you an invoice...

[m_star01]

Originally Posted by Tambohamilton

They could actually be plugged into the wrong connectors - physically switched around

Really bizzare, i only had ignition coils/plugs done to the car in the last year. Would they have messed around with the o2 sensors before cat?

Would there be any errors showing "sensor 1 is in, sensor 2 connection"

[NorthernDancer]

I know very little on this subject but I understand rear cats "monitor" only, they do not send info to the ECU, do not affect vehicle driveability, replacing them will do nothing for you.
The garage you went to, did it have 3 or more BMWs parked there? If not, I would be tempted to try one that does.
Any time you see another BMW owner, try to talk to them about who they use for service.

[gbalthrop]

Originally Posted by m_star01

Still confused how the sensors be reversed is that a term or you actually mean someone swapped them around?

Originally Posted by m_star01

Really bizzare, i only had ignition coils/plugs done to the car in the last year. Would they have messed around with the o2 sensors before cat? Would there be any errors showing "sensor 1 is in, sensor 2 connection"

If you have N43 Engine (or N46 -- you never answered questions in Post #3), I would need to refer to wiring & parts info, as I have NO personal experience with those engines. HOWEVER, on N52, AFAIK, the ONLY difference between Pre-Cat O2 Sensor in Bank 1, and Pre-Cat Sensor in Bank 2 is the LENGTH of the wiring harness. Swapped or Reversed CONNECTORS (which Engine Harness Connector a particular Lambda Sensor is connected to) does NOT require physical removal of Sensor from Exhaust Manifold.

If you would provide the Last-7 Characters of your VIN, I could provide an ISTA diagram of the Location of the 2 Pre-cat connectors and sensors, and you could inspect quicker than this discussion has been.

I just noticed that in your original Post, you had a photo of Scan Tool showing "2A2C" Fault Code. That code can either mean Bank 2 is TOO LEAN, or it can ALSO mean Bank 2 TOO RICH, depending upon DME Variant, other codes, P-code associated with Hex-code, etc. Based on ALL THREE codes (2A2C, 2C7F, 2C6C) best guess is Bank 2 Pre-Cat Sensor Signal, as received by DME suggests fuel mixture is TOO LEAN. Viewing STFT would quickly answer that question.

HOWEVER, until you see the ISTA wiring/ Location Diagrams, and KNOW which Pre-Cat Sensor is plugged into the Engine Harness connector for Bank 2, you don't know WHICH sensor signal DME is reporting as Bank 2. If connectors were SWAPPED, Bank 1 sensor signal would be reported as Bank 2.

You are correct, that except for a few phenomena such as Murphy's Law, Peter Principle, etc., it is UNLIKELY that connectors are reversed. That is only ONE of several things that can cause the three codes in question.

Like a LOT of things in life, what seemed like an insurmountable problem will become LESS so with TESTING & DATA, which hopefully you and your Ancel BM500 can provide. Fault Codes are only the Starting Point for Diagnosis.

So Live Data of Short Term Fuel Trims (STFT) or Pre-Cat O2 Sensor Voltage for BOTH Bank 1 & Bank 2, and whether any deviation is constant or Intermittent, should be the FIRST Step in this case. Those test should be conducted at Warm Idle. Reporting that Data, along with Last-7 VIN is next. Only THEN can the "self-appointed experts" on this Forum have a basis for opinion.
George

[m_star01]

thanks mate, my scanner will come today i will do live data stream to monitor the o2 sensors. From what i understand if they are working correctly they should be ROUGHLY the same values idle/revving. If one is way higher/lower or not even moving with revs then i know its a sensor issue. Is that correct?

my VIN is: A393010

[m_star01]

hello all i ran my bmw scanner (its basic not flashy like the ipad ones BMW have)

attached is the reading i am not sure but the signal o2 sensor behind catalytic converter doesn't move much and seems stuck on 0.41 (sometimes 0.39), even with revving the before sensor moves but the behind sensor seems to be less reluctant to move.

Anyone know why this maybe?

[m_star01]

sorry i am not sure why the graphics so big.

below is when i rev the engine rather than idling

[m_star01]

Anyone got any thoughts on above? 👍👍

[gbalthrop]

Originally Posted by m_star01

Anyone got any thoughts on above? 👍👍

Thoughts:
1) Your 8/2009 build 320i E90 N43 has 3 O2 Sensors: one pre-cat sensor on each exhaust manifold to "Trim" fueling once "Closed Loop" occurs when engine warms, and ONE Post-Cat sensor.

2) In your FIRST Photo of Scan Tool Screen, when I lie on my Left Ear ( ), I see that Bank 1 Pre-cat sensor voltage is 2.04V, Bank 2 Pre-cat sensor voltage is 2.05, and POST-CAT Sensor voltage is 0.40V.

3) In your LAST Photo (Left ear beginning to throb ;-), Bank 1 Pre-cat Sensor Voltage = 3.16V, Bank 2 Pre-cat Sensor Voltage = 3.14V, and Post-Cat Sensor Voltage is 0.41V

A) It would be helpful if you told us WHAT the conditions were at time EACH of those two photos was taken.

B) I am NOT an O2 Sensor Guru, and know NOTHING about the N43 Engine. My SWAG: If BOTH Pre-cat sensors show nearly identical voltage, but BOTH change value significantly (~1.1 Volt) with virtually NO change in Post-Cat Sensor Signal Voltage (0.01V), the FIRST suspect is the Post-Cat Sensor, or it's wiring/connector which should be inspected/ tested FIRST.

C) If your LAST photo was taken after engine warmed, or at RPM > Idle, then that may explain your MOT results. If you MUST resort to throwing parts (due to lack of competent Diagnosis ;-), I would simply replace Post-Cat Sensor (NOT all three), and see if/how data changes. I'll attach ISTA ScreenPrints of wiring & Locations to NEXT Post.

Suggestions from N43/ O2 Sensor Gurus WELCOME!!
George

[gbalthrop]

Attached are ISTA ScreenPrints of N43 Lambda Sensor wiring SSP & Location of Post-Cat Sensor, B62102.
George