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  #1  
Old 03-18-2017, 10:20 PM
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46A4 - DDE: DeNox Catalyst, Understanding root cause

Haven't found a thread with this specific code, thought I would open new one.
Also, cross-posted in that other forum.

2011 35d, 108K miles.

So, this non-CEL fault is lately coming back (triggered a CEL a couple weeks ago, I recorded it and removed from memory to keep an eye on reocurrences):
Quote:
0046A4 DDE: NoX sensor after DeNox Catalyst, plausibility NoX
I have searched potential answers on forums, with potential causes being:
-Bad urea active tank
-Clogged SCR metering valve
-Bad cat
-Bad or fouled NoX sensor

Being fully aware that there is a warranty extension on Active Tank and Metering Valve, I need to make sure those are the culprit before heading out to dealer for claim (and risking wasted diagnostics fee).

So, pulled this fault code documentation in Rheingold:
Quote:
Fault Description
Monitoring the NOx signal offset value (nitrogen oxide sensor downstream of SCR catalytic converter). The fault is detected if the average offset value exceeds a limit value.

Limit value: between 30 ppm and 60 ppm (version-dependent).
This is pure legalese!

Can one of the veterans help me decipher this text (calling you ard, Doug H., ZetaTre)?

This snippet:
Quote:
NOx signal offset value (nitrogen oxide sensor downstream of SCR catalytic converter)
..is it safe to assume that "offset value = difference in reading between pre and post NoX sensor"?

Can it be said this way?:
"The fault is detected if the average detected NoX reduction (over certain period of time, on that below) between pre and post Cat sensor is less than 30-60 parts per million".

Continuing to read..
Quote:
Condition for fault identification
Monitoring takes place continuously when the following preconditions are met:

- The difference between the maximum and minimum offset value must be less than the limit value during this minimum duration.

Limit value: between 4 ppm and 7 ppm (version-dependent).

...
[talks about engine rpm and other preconditions
...
I think it can be said like this in plain English:

"Non-stop monitoring will start as soon as largest and smallest difference between pre and post NOx sensors is less than about 7 parts per million.
In other words, system will start continuous watching as soon as it detects no improvement in NoX.
"

The rest of documentation, more-less understandable.
Quote:
Condition for fault memory entry
The fault is entered if it has been detected more than the following number of times (fault debouncing counter): 1

Action in service
Check the NOx sensor downstream of SCR catalytic converter with an SCR catalytic converter system check.

1. Check line and plug connections
2. If wires and plug connections are OK:
Replace nitrogen oxide sensor after SCR catalytic converter.
Next, hooked up laptop and went for a drive to :
1. Confirm post-cat sensors working
2. Gather live NOx sensor data under various driving conditions

Observations:
40 mph on cruise control, 1,500 rpm, UPHILL
pre-cat: ~600 ppm
post-cat: ~200 ppm

40 mph on cruise control, 1,500 rpm, LEVEL
pre-cat: ~110 ppm
post-cat: ~50 ppm

0 mph, 800 rpm, IDLING
pre-cat: ~130 ppm
post-cat: ~12 ppm

If it means what I think it means, I may have hit this "Limit value: between 30 ppm and 60 ppm" on this test drive:
Quote:
40 mph on cruise control, 1,500 rpm, LEVEL
pre-cat: ~110 ppm
post-cat: ~50 ppm
If that's true, I need to get to the culprit of worse-than-expected NoX readings after SCR.
They could be:
-DEF injection issues
-Bad Catalyst
-Bad NoX sensor. Which one?
For example, pre-SRC sensor could be fouled by soot, giving lower initial readings and thus misleading post-SRC sensor...

It doesn't help that there's no information available for NoX reduction baseline in well-working SCR system in 35d.

Any info is appreciated.
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  #2  
Old 03-19-2017, 03:10 AM
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Doug Huffman Doug Huffman is online now
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Sorry, I am no help. Where are the Test Plans specified that should differentiate among the possible causes? INPA?
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Old 03-19-2017, 05:27 AM
TroubledGnome TroubledGnome is offline
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Quote:
Originally Posted by serge1 View Post

It doesn't help that there's no information available for NoX reduction baseline in well-working SCR system in 35d.

Any info is appreciated.

Assuming that they pre/post values are available in Carly, I have to drive my son back to college this afternoon and could gather some data for you.

I have 102k miles and had the active tank replaced this past summer.
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Old 03-19-2017, 10:38 AM
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Quote:
Originally Posted by TroubledGnome View Post
Assuming that they pre/post values are available in Carly, I have to drive my son back to college this afternoon and could gather some data for you.

I have 102k miles and had the active tank replaced this past summer.
Thanks! That would be helpful.
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Old 03-19-2017, 10:52 AM
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Quote:
Originally Posted by Doug Huffman View Post
Sorry, I am no help. Where are the Test Plans specified that should differentiate among the possible causes? INPA?
Test plan for post-SRC NOx sensor does not determine the root cause.
It merely asks the user to pick from likely cause (recalling from memory now):
-No cause determined
-Broken wire/connection
-Faulty sensor

I picked No cause determined, for my case. It then sets a code value in test plan report:
Quote:
Diagnosis code: D1170_D0000000_10_901
No cause of fault found
Because the test plan leaves it up to the user (read: BMW technician), I would be opening myself up to costly wrong diagnosis.

Having a base line for offset value (e.g. reduction efficiency) for a brand spanking new drivetrain (engine and SCR) would help. It is interesting there's nothing out there for clean diesels - while you would think there would be, with required emissions tests, etc.

For all we know, both sensors and the SCR system may still be working as designed. But, because of potential issues with running rich due to likely injector issues in my vehicle, there could be simply too much NOx produced.

To clarify above: I get blue smoke for about 10 seconds on cold starts, and there's quite a bit of soot on tail pipes. I may need to address that first.
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Old 03-19-2017, 12:42 PM
TroubledGnome TroubledGnome is offline
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I'm back and hope this helps.

https://docs.google.com/spreadsheets...it?usp=sharing

The sheet shows time, but the first 2/3 of the graph is while I had the cruise set at 75mph (2200 rpm) after engine was completely warmed up.

The last 1/3 was on the way home and I first set the cruise at 55 mph for a few minutes and then 60mph for a few minutes and lastly 65mph. I think you can see the steps in the graph.

On average when the Pre was 200ppm the post was 85ppm while cruising on flat freeway at steady speed. A 5% steady grade at the same speed averaged a pre 250ppm and post 125ppm

I noticed a few things. When you drive at 55-60 mph the scr appears to be very efficient keeping the post NOx values well below 30ppm. When you drive at normal free way speeds 70+ mph the efficiency appear to be 50% - 60% for pre and post NOx readings.

I also noticed that when you drive around town a bit and then get to the freeway the NOx will stay pretty low for about 5-10 minutes due to what I'd assume heavier dossing in town and taking some time to burn off the extra DEF in the SCR.

Anyway let me know if that helps or if there is another parameter that would help and I'll see if I can track it again later this week.
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Old 03-19-2017, 02:50 PM
Thirdy Thirdy is offline
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Quote:
Originally Posted by serge1 View Post
-Clogged SCR metering valve
-Bad cat
-Bad or fouled NoX sensor

Being fully aware that there is a warranty extension on Active Tank and Metering Valve, I need to make sure those are the culprit before heading out to dealer for claim (and risking wasted diagnostics fee).
you can actually check your metering valve using rheingold. It will activate the valve and you will hear a clicking sound. You can also remove the metering valve and clean it using a 9v battery and a can of carburator cleaner to check if it is still spraying.

I got these test leads at harborfreight (only used 1 of those)

http://www.harborfreight.com/18-inch...ads-66717.html

and followed this

http://www.harborfreight.com/18-inch...ads-66717.html

but I used an electrical tape wrapped around the long plastic nozzle instead of the tire valve inserting it to the metering valve.

Last edited by Thirdy; 03-19-2017 at 02:52 PM.
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Old 03-19-2017, 10:52 PM
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Quote:
Originally Posted by TroubledGnome View Post
I'm back and hope this helps.
Very much appreciated. Thank you!

The freeway (55+mph) values look close to what I remember seeing. Good to know.

Quote:
Originally Posted by TroubledGnome View Post
Anyway let me know if that helps or if there is another parameter that would help and I'll see if I can track it again later this week.
It would help me seeing your values for 40pmh straight and uphill, both on cruise control (RPM expected around 1,500).

40mph uphill is when I was seeing difference below 60ppm for my vehicle. I have to assume that is when system wakes up and starts keeping an eye on it.

P.S. Wish Rheingold had values recording. Should probably look into Carly .
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Old 03-21-2017, 09:19 PM
ChrisM011 ChrisM011 is offline
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I will add some values to this discussion.
Background: I have had many emissions-related problems with this vehicle. So many, I am not sure why I still have it. Anyway, that is another story. My X5d has brand new pre- and post-cat NOx sensors and a new SCR catalytic converter 12 months ago. Total mileage on the vehicle is just over 86k. The trip in which I performed the data logging was my commute home from work. I live in the Sacramento area, so temps today were mid 60s. Most of my drive is freeway. Thermostat was replaced last year and coolant/engine temps for all test data was around 90 deg C.

Idle values, taken at the end of the drive, sitting in the driveway: Pre-cat values ranged from 67-72ppm, post-cat values were between 4-5ppm
Cruising at approximately 70-75 mph indicated on speedo: Pre-cat values 120-130ppm (no cruise control, approximate range), post-cat values between 23-26ppm
Other freeway cruising values: pre-cat values around 110ppm=post-cat values around 19ppm; pre-cat values around 90ppm=post-cat values around 12 ppm
Heavy throttle uphill pre-cat spike to 795ppm=post-cat spike to 379ppm

As I mentioned, the NOx sensors were both just replaced. They were replaced only 12 months ago by BMW, so the new ones were covered under the 2 yr parts warranty. Frustrating to have them go bad after only about 15k miles. I am concerned I have an underlying problem causing this, but the only way to find out is to compare data!
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Old 03-22-2017, 09:59 AM
RPsX5d RPsX5d is offline
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ChrisM011 - thanks for the post.

Assuming I read your post correct, you now have a brand new NOx sensors (pre and post) and your SCR system is only 12 months old.

The pre/post delta ppm you show is much higher than the expected 30-60 ppm (per OP's first post on this thread, included below). If the 30-60 ppm delta is correct, is your system overdosing the urea/DEF? i.e. a large injection of DEF results in a bigger than expected drop in ppm between pre and post NOx sensors.

I don't know how all this works, just wondered . . .

Second, are you using the Carly app to monitor this or the Rheingold? The reason for asking - I am also trying to track these ppm figures . . . but I would also like to see what the EGR valves are doing (both low and high-pressure EGR valves) . . . I still haven't found the EGR valve parameter on Carly parameter list . . . did anyone find it?

Thanks.


Quote:
Originally Posted by serge1 View Post
. . .

This snippet:

..is it safe to assume that "offset value = difference in reading between pre and post NoX sensor"?

Can it be said this way?:
"The fault is detected if the average detected NoX reduction (over certain period of time, on that below) between pre and post Cat sensor is less than 30-60 parts per million".

Continuing to read..

If it means what I think it means, I may have hit this "Limit value: between 30 ppm and 60 ppm" on this test drive:
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Old 03-22-2017, 10:53 AM
TroubledGnome TroubledGnome is offline
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Quote:
Originally Posted by serge1 View Post

40mph uphill is when I was seeing difference below 60ppm for my vehicle. I have to assume that is when system wakes up and starts keeping an eye on it.

P.S. Wish Rheingold had values recording. Should probably look into Carly .
I wasn't able to log it, but cruise set at 40 and a steady uphill climb for 2 minutes gave an average of 700ppm pre scr and a 400ppm post scr

On a flat road at the same speed gave an average of pre 125ppm and a post of 35ppm.
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Old 03-22-2017, 11:06 AM
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Quote:
Originally Posted by TroubledGnome View Post
I wasn't able to log it, but cruise set at 40 and a steady uphill climb for 2 minutes gave an average of 700ppm pre scr and a 400ppm post scr

On a flat road at the same speed gave an average of pre 125ppm and a post of 35ppm.
Excellent, thank you!
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Old 03-22-2017, 01:47 PM
ChrisM011 ChrisM011 is offline
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You read my post correctly, RPsX5d, my emissions system is basically new. That is what makes this data somewhat interesting (assuming the associated systems are functioning correctly).

I am monitoring using Carly. I have yet to do anything with Rheingold.

My understanding of the system is that the delta between pre- and post-cat NOx sensors should be greater than that 30-60ppm value. I believe that when values fall within that 30-60ppm range the DDE recognizes a fault and will then set the CEL. If these assumptions are correct, I do not believe that my X5 is overdosing DEF. my particular car has never used DEF at a rate that seems accelerated and the recent fix did not have an accompanying software update.

Another observation: when I got my last CEL, I was live monitoring (not logging) the NOx sensor data. Same drive as my logging from yesterday, similar conditions. Pre-cat NOx was around 120ppm while post-cat went as high as 60ppm or so during light throttle changes. I think my CEL related to the delta falling within that 30-60ppm range.


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Old 03-23-2017, 09:47 PM
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This afternoon, while weather has improved, decided to run the SCR exhaust emission system system test (no, "system system test" is not a typo!).

It is a pretty intensive test, keeping engine RPM at 2,000 for 45 minutes.

Here is the Log:
Quote:
SCR exhaust emission system system test
>Function test: SCR system.
>Functional check: start the scr system.

6:23pm. Engine rpm went to 2K
6:30pm. RPM went to 2.1K

-- Output ----
SCR functional check - Step 4/11: Relieve the SCR catalytic converter
Relieving the SCR catalytic converter. The stored NH3 in the catalytic converter will be eliminated completely. This step takes:600s (10 minutes)
Remaining duration: 600 s
Note: The exhaust temperature will be increased to up to 450 C! Make sure the exhaust gas is extracted correctly!
Temperature before oxidation catalytic converter: 323.24C
Temperature before SCR catalytic converter 177.57C
Note: The diagnosis system display window may not update.
This test step is expected to be completed at: 06:40:06hh:mm:ss
Please wait!
----

6:40pm: rpm went back to 2K

--- output ---
SCR functional check - Step 5/11: Cool down the exhaust emission system
Cooling down the exhaust emission system to approximately 220 C.
The cooling-down period is 500 seconds (approximately 8.5 minutes).
Temperature before oxidation catalytic converter: 228.56C
Temperature before SCR catalytic converter 331.35C
Test step remaining time: 439 s
Please wait!
-----------

6:49 rpm dropped to 1.5K

SCR functional check - Step 6/11: Adjustment of the nitrogen oxide sensors
The two nitrogen oxide sensors will be compared to each other.
Nitrogen oxide sensor before SCR catalytic converter: 110.9ppm
Nitrogen oxide sensor downstream of SCR catalytic converter: 123.0ppm
Please wait!
---
6:50 rpm went to 1950

-output--
SCR functional check - Step 7/11: Fill the SCR system.
The SCR catalytic converter is preheated for .
Time elapsed:0*s
The exhaust temperature is raised to 220 -* . The operating mode for the engine will be switched to pre-heating.
Exhaust temperature upstream of the oxidation catalytic converter:175.44*C
Notice!
The diagnosis system display window may not update.
This test step is expected to be completed at: 06:51:55hh:mm:ss
Please wait!
-----------
6:57 pm rpm went to 800 normal.

6:58 system stopped the engine.

--- output --
SCR functional check - Step 11/11: Evaluation
The following values have been found:
Duration of the functional check: 2076 s
Starting conditions:
Engine coolant temperature: 57.96C
NH3 loading of SCR catalytic converter: 0.02g
Temperature sensors, first measurement:
Exhaust temperature upstream of the oxidation catalytic converter: 181.38C
Exhaust temperature upstream of diesel particulate filter: 193.00C
Exhaust temperature before SCR catalytic converter: 159.05C
Temperature sensors, second measurement:
Exhaust temperature upstream of the oxidation catalytic converter: 170.0C
Exhaust temperature upstream of diesel particulate filter: 187.0C
Exhaust temperature before SCR catalytic converter: 153.7C
NOx sensors:
Relief period: 600 s
Nitrogen oxide sensor before SCR catalytic converter: 108.37ppm
Nitrogen oxide sensor downstream of SCR catalytic converter: 120.63ppm
Ration of NOx sensors:*0.832
SCR catalytic converter/nitrogen oxide volume check:
Soot mass in the diesel particulate filter:5.74
Calculated threshold value {ETA}: 0.73
Diesel particulate filter regeneration status:False
Marker regeneration status: 00
Nitrogen oxide sensor before SCR catalytic converter: 118.42ppm
Nitrogen oxide sensor downstream of SCR catalytic converter: 87.04
Exhaust temperature before SCR catalytic converter: 260.34C
NH3 loading of SCR catalytic converter: 0.35g
NOx conversion ratio: 26.50 %
SCR long-term adaptation factor: 0.998004
SCR catalytic converter total ageing factor: 0
SCR catalytic converter ageing factor temperature: 0
Press Next to continue to the result of the analysis.

--------------
>next

SCR functional check - Step 11/11: Evaluation
The SCR functional test is finished.
A fault was detected for SCR catalytic converter.
Replace the SCR catalytic converter.


End test module
---

SCR functional check - Step 11/11: Evaluation
The SCR functional check entered the following fault memories:
40D4
46F2
4BDA
The*fault memories can be deleted.
------

Notice!
Carry out the following service functions depending on which components have been renewed:
Urea/water mixture: SCR system: Adjustments: NOx sensors
NOx sensors: SCR system adjustments: NOx sensors
SCR catalytic converter: SCR system adjustments: SCR catalytic converter
Metering module: SCR system adjustments: SCR metering module
The corresponding service functions were added to the test schedule.

------

done.
So, the test automatically determined SCR catalytic converter is doing its job not efficiently.

I do wonder if this determination was due to the fact that downstream sensor itself is near end of life (as many of us suggested it being a 50K mile maintenance item, really), and thus unable to properly read measurements.

Then, SCR test is in turn receiving bad data, as there is nothing to rely upon but the 2 NOx sensors.

Snippet in question from log above:
Quote:
Nitrogen oxide sensor before SCR catalytic converter: 118.42ppm
Nitrogen oxide sensor downstream of SCR catalytic converter: 87.04
NH3 loading of SCR catalytic converter: 0.35g
NOx conversion ratio: 26.50 %
((87.04 ppm /118.42 ppm) -1) * 100 =26.5

Anyway,
Using arguments below:
-Life expectancy of NOx sensor is 50K miles.
-SCR faults are based on NOx sensor readings

... bit the bullet and ordered the NOx sensor from BMW of Bridgewater ($220).

When it arrives, will install and calibrate, clear codes and run SCR function test again.

Will see!

Last edited by serge1; 03-23-2017 at 09:51 PM. Reason: full log
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Old 03-24-2017, 11:49 AM
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Quote:
Originally Posted by serge1 View Post
... bit the bullet and ordered the NOx sensor from BMW of Bridgewater ($220).

When it arrives, will install and calibrate, clear codes and run SCR function test again.

Will see!
Well, bummer. BMW of Bridgewater no longer carries the older part # 13628511666 in stock. Refunded my order. They have one in stock for $550. Still a better deal than elsewhere for 700+

Going to hold on for a little. Maybe take out the existing, clean it.
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Old 03-25-2017, 07:12 AM
Thomv Thomv is offline
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Try these guys. Always have been quite reasonable.
https://www.ecstuning.com/?utm_sourc...ECS%2520Tuning
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Old 03-27-2017, 01:53 PM
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Try these guys. Always have been quite reasonable.
https://www.ecstuning.com/?utm_sourc...ECS%2520Tuning
Thanks. Same $550..
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Old 03-28-2017, 02:41 PM
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Quote:
Originally Posted by serge1 View Post
40mph uphill is when I was seeing difference below 60ppm for my vehicle. I have to assume that
Looks like I made a mistake here earlier. Checked back with my logs.
Lowest difference betwen upstream and downstream was on LEVEL.

I even said it later in another post:

Quote:
40 mph on cruise control, 1,500 rpm, LEVEL
pre-cat: ~110 ppm
post-cat: ~50 ppm
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Old 03-28-2017, 03:08 PM
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Update.
Took out the downstream NOx sensor last night. Found it to be covered in soot, same soot that covers my tail pipes.
It is not oily, but very fine. Easily wipes off, though.

I am getting convinced that this soot is the cause for NOx sensor failure, and worse, doing same to SCR catalyst.

So, placed the sensor in sonic jewelry cleaner, along with alcohol/water mixture. Took out, sprayed with brake cleaner, back into sonic cleaner.
Saw dirt/soot/stuff come out of the tiny holes - good!

Dried it off, put back in and went for a drive to calibrate and check ppm measurements under same LEVEL, UPHILL and IDLE conditions.

I did see (well, hear, my wife was doing the reading) values for downstream sensor that were better than last time, but not by much. I can say that on LEVEL, where I used to see difference of 60 often, difference on low end stayed above 80.

It could be anecdotal evidence, but I am curious about running yet another SCR test, to see if anything improved.
For following reason:

-Downstream NOx will stay clean for some while.
-I was running low on DEF during last SCR test. After last SCR test (50 minutes of basically idling at 2K RPM), next day, low DEF warning popped up.

The goal now is to pin point the cause.

From SCR test documentation:
Quote:
Possible causes of fault:
-Urea/water mixture quality deficient, misfuelling, SCR active tank empty
-Nitrogen oxide sensors faulty (poisoned, sensor drift)
-SCR catalytic converter faulty (not enough nitrogen oxide is converted)
-Metering module faulty (too little urea/water mixture metered in)
-SCR tank system faulty (too little urea/water mixture metered in, system pressure in the metering line is too low)

Fault elimination measures:
-Check urea/water mixture quality
-Remedy all SCR system faults
-Completely top up the SCR active tank, check the filling level using the diagnosis system, if applicable, activate SCR top-up identification using the corresponding service function

Note: reset long-term adaptation. Carry out the service function SCR adjustments and adaptations. Select the menu item Diesel exhaust fluid changed, reset wrong media. (long-term adaptation factor)" in the service function.

-Carry out a conditioning run with the following driving profile:

- If the residual running distance is less than 90 km (55 miles). the residual running distance can be extended once with the service function SCR reset.
- Drive for one hour at constant speed with phases of slight engine traction and at a speed of approx. 70 - 90 km/h.
- If conversion of the nitrogen oxide exhaust gases can be performed successfully, the Check Control message on the instrument cluster goes out. The warning and shutdown scenario faults have been remedied and can then be deleted.

- Note: The driving time is one hour, both nitrogen oxide sensors must be enabled. Only then is a system check performed. The enabling can be checked with the diagnosis system. Depending on the exhaust temperature, the nitrogen oxide sensors are enabled within 15-35 minutes.

-Delete fault memory with the diagnosis system.
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Old 04-23-2018, 05:37 AM
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Serge, has the 46A4 code come back since cleaning the downstream sensor?
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Old 04-27-2018, 12:53 PM
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Mein Auto: 2011 BMW X5 35D
Quote:
Originally Posted by hsindogg View Post
Serge, has the 46A4 code come back since cleaning the downstream sensor?
Yes, it did. After deleting the code, it would come back in less than 500miles, normally.
P.S. Since January of this year, I deleted DPF/SCR/EGR, replaced DPF with custom DOC.
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