Xentry Diagnostics Value 751 - Factor for adaption of component 'NOx sensor upstream of SCR catalytic converter'

[EdPhil]

I think I should say that I have not gone a bit quiet because I have decided to drop this. As I have not managed to get any NOx graphing details etc. yet from anybody who has installed upgraded NOx sensors (I am of the opinion that garages just fit and hope without operational testing and graphing), and Xentry is (in my opinion) not designed to provide very detailed diagnostics of components, I am diving a lot deeper into the individual ECU units' software with more sophisticated diagnosis tools. This takes a lot of time but is also very enlightening - still working on it.

Another thing I have been doing is checking the NGK and Continental patents, which should be detailed enough to know exactly how the Control Unit and Sensor work together - again, still working on it. However, I have a pretty good understanding now of how the sensor ceramic chip (the bit at the heart of the sensor) is manufactured and works, and what those eight wires are for - that's a question lots ask on the internet, but I have not seen anybody answer properly yet!!

I have been servicing the CLS this week, so its been in my garage and not done any mileage.

Best Regards:

Edward

 

[Botus]

new bit of fun (USA region info)

Feb 2023

2012-2016 Vehicle Model E-Class, GL-Class, GLE-Class, GLK-Class, ML-Class - the coding of the control units for selective catalytic reduction (SCR) and fully integrated transmission control (VGS) do not correspond to the specifications as part of the “BlueTEC update” diesel field measure. This could result in the CAL ID (Calibration ID) not being read out from the vehicle and re-documented in the relevant systems. This situation does not have any additional technical implications for the vehicle.

MBUSA will conduct an Emission Service Campaign in which an authorized Mercedes-Benz dealer will update the SCN coding for SCR and VGS on the affected vehicles.

2022020024 Mercedes-Benz Technical Service Bulletin

2022020024 Mercedes-Benz Technical Service Bulletin

www.tsbsearch.com

 

[EdPhil]

Botus - I did read your post last month. It's not that surprising now that I have had a more detailed look into the control units. I have gone deeper than Xentry using Monaco DTS and the CDI ecu seems quite happy (with only the 2021 software update) to recognise the changed NOx control units and calibration IDs installed without any need to actually do any SCN coding - meaning they are recognised and work without being forced to do the coding. I had got information from somewhere that the SCN coding was really only necessary so that the detailed datacard got updated, as I understand that there are some regulations that say all changes to emissions related systems must be documented. It all seems very silly for a NOx system that does not become operational until you have driven about 10-15 miles. What's the point of that for the driver who commutes 15 miles to work and back? His vehicle is no more 'eco-friendly' for his commuting than my E-Class without the BlueTec.

Anyway, my CLS has now covered about 400 miles on various journeys and there have been NO NOx related error codes whatsoever so far. So that's just (well eventually after trial and error) by fitting two second-hand QO5 control units (approx £90 each with NGK sensors fitted), removing the used/refurbished NGK sensors and wiring-in two new Lautro sensors (£50 each). So, my time and about £300 - other spend on trial and error and more software probably doubles that.

I have spent a lot of time going through Continental and NGK patents to try and ascertain if the sensors are calibrated to the control units, but have not managed to confirm that one way or the other yet. The patent information I have seen details the original designs of control units and sensors as separate items and then there are many more additional patents as the Companies 'improve' their designs to overcome the problems they (and us users) have experienced. I have not found exact details of the precise models fitted to my CLS, but some are pretty close.

When Continental decided to hard wire an NGK sensor to its control unit they called it a 'Smart NOx Sensor'. So, that's what they should be called as simply 'NOx sensor' for the combined unit has always been misleading.

What is interesting is than NGK's latest ceramic chips have a coating around the tip, which is open to the elements in the sensors I have cut open. This is to protect the sensor from water damage. Continental were also granted a patent in 2022 for a connector plug between the control unit and sensor lead as they had 'recognised' a requirement for one.

As the original sensors only had six wires, I cut open a couple of the old sensors I have (had) to check exactly how they were built (photos attached), and slowly ground down the ceramic chips to see exactly which component each wire connected to. I am still working on that when I have the time, but I am almost there. Note that the ceramic sensor, which is the heart of the unit is very small and the electrical conduits and parts are formed in pastes sandwiched between six substrate levels that are 'baked' together. I don't have time to explain all the detail now, but the heater wires are Orange and Black and the Blue wire is connected inside the chip to the Orange side of the heater circuit - possibly for temperature or failure sensing purposes. Every sensor I have had apart from one has has similar resistance readings across the heater.










Although I am getting no NOx sensor errors, the graphing when operational is still illogical with the rear sensor showing higher NOx ppm levels than the front sensor. I wondered whether this might just be a programming error and the sensors data had been switched erroneously due to the inconsistent nomenclature Mercedes apply to these sensors in their documentation - I can explain in detail if anybody is interested. So, I installed the July 2023 version of Xentry to see if that had any differences. The graphing of the operational sensors is still the same, but the teaching-in of replacement sensors can now be done on an individual basis instead of both together. It did not appear to work (well no confirmation message) with my sensors, but I only attempted it once. HOWEVER, when compiling a custom list of actual values that included VALUE 751 I got a message that some actual values are NOT VALID for this variant (meaning the state of my CLS' ECU), so that could be the answer to my orinal query, but still begs the question 'why not?'.

I have been collecting all the latest Daimler files needed to interrogate ALL the exact (rather than generic) ECUs with Monaco DTS and will then be able to look at every query and response communication between the ECUs and the actual data received from the sensors more easily than I get with an oscilloscope or Xentry.

Monaco DTS also appears to have a set of routines for proper testing of the SCR system and its components, and I will be looking at that soon to tailor it to my CLS.

Lastly, I finished a major service on the CLS recently and it sailed through its MOT last week. However, it also needed some bolts changing on the power steering motor as part of a Mercedes safety recall and I took it in to Sytner last Friday. One of the bolts had failed and it's still with them as, apparently, it now needs a new or reconditioned steering rack that may take some time to obtain. - Mercedes are supposed to be paying. I would
just drill and tap the snapped bolt out - probably what will happen to this rack anyway before somebody else gets it(?).

I hope that's of some interest.

Best Regards:

Edward

 

[Botus]

not sure I follow all the technical detail but one bit concerned me - seems all CAT sensors sniff outside air via those 4 external holes as part of their normal operation... not 100%, but I think so they have a base reference to whats happening on the inside.....

FYI maybe this is helpful on the ins and outs of how a Petrol engine does its fuel mixture.... (its not my work - someone wrote it on a thread I started and i plagiarised and turn some odd language ans terminology into "English"

 

[Botus]

Petrol Engine "Lambda, fueling and AF-XIED for Dummies" by knutk on ukgser's site, with minor tweaks by me

Emission regulations require engines to limit pollution. It's a fairly complex picture, but let's focus on the subject that annoys us, the fueling of the engine, or rather, a lack of fuel it needs to run well.

Background: Lambda vs AFR (air fuel ratio)
In an ideal world, perfect combustion for an engine is when every drop of gasoline finds an oxygen molecule to bond with, so when the mixture is ignited, every drop of gasoline burns, with no excess.

To understand how well the vehicle is coping (with the fueling its receiving from the various parameters its measuring, mapped to a list of what to inject under which conditions), it analyses the combustion. To do this the manufacturer installs an O2 sensor in the exhaust system. The O2 sensor reacts to the amount of vacant (unused) oxygen molecules. And when there's no remaining oxygen in the exhaust, this condition is defined as Lambda 1.0. For a gasoline engine, Lambda 1.0 will be reached when the AFR is at the stoichiometric 14.7:1, i.e 14.7g of air to 1g of gasoline.

So why mess with Lambda, rather than the AFR?
The O2 sensor is searching for excessive oxygen. Different types of gasoline (with ethanol etc) may offer different AFRs. However, regardless of what type of gasoline the engine is burning Lambda 1 will ALWAYS be the condition where all the oxygen is used up.

To reduce confusion, we'll stick to common gasoline offering an AFR of 14.7 for Lambda 1 and debate how a Narrow band (NB) O2 sensor works in BMW boxers up to the introduction of the 1250 shiftcam engine - (which uses a different sensor type.)

The Picture below is borrowed from NightRider who produce the AF-XIED. Its showing the output of a Narrow Band sensor when warm, where the O2 sensors emit voltage in accordance with this chart below.

The scales of AFR are adjusted to reflect gasoline that produces Lambda 1 at AFR 14.7 and the picture shows the varying O2 sensor voltage outputs when subjected to differing AFR values. The three different coloured curves show the voltage output also changes with temperature. Noting, when you look along the 0.5V line, all three curves deliver the same voltage around an AFR of 14.6 - 14.8.

The ECU uses this O2 sensor feedback to know if the engine is running too lean or too rich. Whilst expecting the standard engine map and its long term adaptions to land a voltage from the sensor around 0.5V / 0.6V (AFR 14.7). With a 0.8V output, the AFR is down to 14.2-ish. and from there on, the voltage reading vs AFR become less accurate. However the ECU isn't interested in the voltage and doesn't care if its above or below 0.5V. The ECU only sees richer than or leaner than the AFR 14.7 target (even when the voltage output slightly varies with AFR in a highly non-linear manner).

When running, the amount of fuel injected is calculated from tables inside the ECU (called maps, hence remapping means changing the value in these tables). The tables offer information on how long (time in milliseconds ) the injectors are to be opened, depending on RPM, throttle position etc. There are actually several maps, but for simplicity lets just say there are preinstalled maps.

So fuel is delivered according to the maps. However, in order to fine tune the fueling, the O2 sensor offers feedback on the combustion. These small adjustments, called for by the O2 sensor, are called Short Term Trim, and it is basically a number that adds or subtracts to whatever time value is being used opening the injectors.

But keep in mind, the exhaust reflects the result after the combustion, i.e the O2 sensor will not tell ECU what to do. It tells the ECU how it did. Let's say the air filter is clogging up, restricting the airflow to the cylinder. Now, the pre-determined values from the maps will give the engine too much fuel, since the engine gets less air than expected. And the O2 sensor will tell the engine that the fueling is too rich, thus it needs to trim down on the amount of fuel. In a steady condition, this will work pretty well, but it will always need a couple of strokes of the piston in order to first analyse, and then inform if too lean or rich in a continuous process on and on.

Now if its always getting things wrong and having to try and react, that's pretty stupid. So in comes the Long term trim (adaptions): At every condition (rpm vs throttle position) required Short term trim changes get saved in small steps to improve the starting point long term. So, if a given condition consistently calls for adjustment, its gets stored in the Long Term Trim table. This table thus becomes an element of the equation the ECU utilises alongside its other maps (cold temp, altitude variations, pressures, fuel quality etc.) of how best to provide its perception of the correct fueling for a given condition. BMW calls this Long Term Trim the Adaptive map. Its the map that gets zeroed out whenever BMW talks about restoring the adaptive values (wiping the adaptions), and will take around 250 miles before its close to optimal again.

So, what does the AF-XIED do, and how?
If we take a look at the curve below, the curve shows the voltage from a warm O2 sensor, and this is what the ECU receives. (Data from a -15 LC boxer) with time in seconds along the bottom

Up to 10 seconds, the engine is running on a steady throttle. After 10 seconds the engine is accelerating.
In the first 10 seconds, the voltage from O2 sensor flickers between 0.1V and up to 0.9V. When the voltage is < 0.5 V the ecu notices its 'Lean' and it will add a small amount of fuel. Then it keeps adding fuel until the O2 voltage reads >0.5V. Now it's too rich, so reduce the fueling. This is done by correcting the short term trim.

At the 10 second time mark, the throttle is opened up. Now we see that the voltage jumps up to a steady 0.9V. Refer the table of O2 sensor voltage output vs AFR. The green curve reflects the 1200F temp of the O2 sensor, a fairly common condition, i.e when adding throttle, the AFR is richened to 13.6.
What is the big deal about 13.6? Well, the world is not perfect, hence in order to utilise all the oxygen molecules, we actually need to throw in some extra fuel for good measure. Practical tests have shown that adding a bit more fuel will make sure all the O2 molecules get their share of gas, and more molecules with fuel + O2 mixed means a more powerful burn during combustion, i.e more power

Any tuning of the engine that only involves controlling the fuel to air mixture will offer very little additional top end power, as the ECU OEM fueling already offers the added "overfueling" at full throttle (as full throttle has never been the focus of emission control, even if that may change in the future). Tuning that's altering the manufacturer AFR, will be a benefit when the throttle isn't fully open. As in the condition in the first ten seconds of the chart above. And generally, when the throttle is opened up in the higher range (the limit varies depending of the type of engine).

Here is where the AF-XIED shines:
Have a look at the chart below. It shows what the AF-XIED at setting 8 does to the engine.
Red curve is the voltage from the O2 sensor and now being analyzed by the AF-XIED, the blue curve shows the voltage produced by the AF-XIED and transmitted to the engine.

The Voltage from the O2 sensor (the red line) is read by the AF-XIED, and it stops this data reaching the BMW ECU. Instead the AF-XIED analyse the voltage creating the blue curve, and transmits this to the ECU. The ECU has no knowledge about the fitment of the AF-XIED, and behaves as if its the direct feedback from the O2 sensor.

Remember: High voltage = Rich. Low Voltage = Lean.
If we amplify the red curve, we will notice that every time the red curve drops below a straight line, the AF-XIED signals a low voltage to the ECU (And Low voltage = Lean condition). The ECU gets a Lean condition signal and reacts to it by richening the fuel. However we don't want the fuel to go excessively rich, so when the red curve rises slightly above the straight line (hence going too rich), it's time to stop the ECU richening the fuel mix. And this is done by the AF-XIED increasing the voltage emulating the O2 sensor, where the AF-XIED voltage output follows the actual O2 sensor voltage and sends this to the ECU. The ECU will then react to this richer than 0.5 V condition by once again starting to lean the mix, and on and on....

As the AF-XIED tweaks can create over fueling when set up wrongly, it worth understanding how CATs operate.
The OEM variation between lean and rich being so slow actually does not reflect the Bosch ECU's ability for accurate control. Rather its a deliberate need to feed the CAT with oxygen (as CATs use oxygen to convert CO to CO2). This oxygen is delivered to the CAT through the exhaust gases and its controlled to produce periods with excessive O2 in order to feed the CAT. Hence the slow reaction time is to allow for periods with high levels of oxygen. So you should set the AF-XIED to a value rich enough for smooth running, and no more. It's why they recommend going from a low value and slowly increasing richness during set up, one step at a time. And the point of allowing time (100 miles or more) between each change, is that its allowing the ECU to rebuild the Long Term Trim each time the setting has been changed. Note: these only save to the ECUs adaptions if the key is off for 10 seconds (and I believe after reaching operating temperature and its been run through all gears).

 

[EdPhil]

Botus:

Thanks for the reply. It's nice to find someone who also likes a bit of detail. I have a lot on today, so I don't have time to fully read and digest the information you have supplied now, but can spend half an hour or so with a shortish response.

Firstly, the notes about SCN coding mean that I believe the Diesel Software Updates that have been installed on my CLS don't seem to enforce coding for the sensors' control units and possibly other control units as well. Xentry requests that it be done but it just looks like a request so far. I suspect it's a similar case with what the USA regulators have recognised as per your post above, and also suspect there will be more software updates to enforce that coding in future.

The NOx sensor chip samples the exhaust air in through a small slot in the end that is exposed to the chamber supplied by the holes in the casing. Obviously, this is the end of the sensor that is screwed into the exhaust. Reference air is taken from the opposite end of the chip through an even smaller but much longer slot. This end is where the electrical connections are and that air is isolated from the exhaust gases outside the exhaust system. I attach a couple of photos of the tip ends I took and an extract from a patent document that is a schematic very close to the chips in my CLS' sensors. Note that the reference air slot is in the layer adjacent to the intake slot layer, so you can orientate the photos with the schematic diagram. I should also mention that there are six layers of substrate, but two are joined without any components between them and the heater layer sits on top of those two. In the Continental picture above that contains a ceramic chip, you are looking at the top layer with the input end at the bottom, and what you can see is the Outside pump electrode of the first chamber and its connection (red wire).

My interest in going this deep was to identify the cables and see if there was an easy test (e.g. the heater) method to check the sensor. I am now of the opinion that the pump cell/s in these unprotected inlet chips are more susceptible to failure though. I have not quite fully fathomed-out all the connections to the wires yet, as the schematic diagram is a bit different from the 'as installed' connections and at fractions of a millimeter in size and distance from each other they are very hard to trace. - It's just the reference electrode connections remaining. When I am done I should have reference resistance and voltage figures for the control unit (I powered one up off the vehicle) and the sensor and a scaled CAD drawing of the sensor layers. If I can be arsed, I may produce a 3D model of the sensor chip, just to keep my hand-in at CAD modelling.

Apologies that the patent drawing has indirect annotations, so all the components are not explained here. I may produce one with direct annotations in future. However, 10 is inlet air and 43 is reference air. 23 is the outside (first) pump electrode. 51 is the auxiliary (second) pump electrode. 44 is the measuring electrode. 42 is the reference electrode. 70 is the heater. Note that there are diffusion control parts (11, 13 and 30) that provide diffusion resistance and separate the cells. I did note that there was a small hole from the heater layer to the reference air chamber that the reference electrode sits in when I was grinding down a chip, and, later when I found the patent document found that also shown in this schematic (if you are wondering what that is, as it's not annotated) - warms the reference air(?). The substrate layers are made of an oxygen ion conductive solid electrolyte, Zirconia.








Got to go!! Took a bit longer than anticipated.

Best Regards:

Edward

 

[EdPhil]

Botus:

I read the detail you supplied last night. Thanks. Basically, I am of the understanding that this explanation is in relation to an 'AF-XIED', 'tricky teddy' device(?) that attempts to redress the sacrificing of engine performance for emissions compliance. Just replacing the NOx control unit PCB with a custom unit that produces 'model' signals irrelevant of what the sensors say would be one such 'tricky teddy' device.

I also reread your comment again, and may have missed the point of your concern about the technicalities of my post with regards to the recent end protection patents for the sensors. I believe I have seen them for both Oxygen and Nox (basically a double oxygen) sensors. It's not anything that covers the exhaust inlet to the holes, but rather a layer added to the tip of the ceramic chip to prevent moisture damage, plus a few additional 'improvements' and modifications necessary because of the new layer. In the ceramic chips installed in my CLS's sensors, the first chamber outside pump electrode seems the most vulnerable.


I have attached a copy of the American version of this patent so you can read it all for yourself.

I have also been led to believe that the steering rack motor repairs to the CLS may take some time to effect due to lack of a spare. My next plan was to separate all the control units I have from the sensors I have and crimp connect 8-pin waterproof auto connectors to each of them so that I can quickly swap all sensors and control units about without having to resolder. That way, I can probably test the whole lot in various combinations in a couple of days to see one way or another if just replacing sensors cause any problems (the cheapest NOx sensor fix). I am aware that there may be some 'learn time' involved, but will fathom that out later. However, I can't physically test the SCR system any further until I get the car back.

Best Regards:

Edward.

 

[Botus]

yep - the last bit I posted was 1) explain how a Petrol engine does its fueling, and 2) how a little extra fools the ECU in to supplying enough petrol so a Biker stays upright, rather than it coughs and splutters and they wobble about due to stupid emission regs

it was only after reading that that I realised full throttle has no emission control at all !!! .... so we'd get more planet savings if we controlled the bit that matters rather than just make engine run badly round town...

 

[EdPhil]

All: That's if anybody is still following - by the number of views of attachments there seems to be little interest in this level of detail. Please let me know if anybody is still interested. In amongst all the waffle are some details that answer some questions people ask that I keep coming across in my internet searches.

Well, I got the CLS back from Mercedes about six weeks ago with a brand new steering rack fitted at Mercedes' expense - I think I would have just extracted the snapped-off bolt, myself! I was busy working on some shed building at the time so the car just sat on the drive for a couple of weeks.

I ran up to Heathrow and back early November in the CLS (Euro 6 is ULEZ compliant) and on the way back the MIL illuminated (about 700 miles since a NOx fault). On investigation it was an AdBlue quality fault. I tested the AdBlue with a reflectometer and it was 32.5 (as new - fine), so I just put it down to the NOx sensors readings being screwy (rear readings higher than front) and cleared the fault. The same day I split all the sensors and control units and fitted 8-pin plugs and sockets to them so I could quickly swap them over to test different combinations. My reasoning for this is that if the new sensors I have (four off) are showing different readings on the same control unit then it's likely that the control unit and sensor combinations are factory hard-wired and calibrated. If that's the case, just swapping in new sensors (the main facet of my investigations) is unlikely to ever be successful unless I can recalibrate the control units - I will look into that later as it must be possible somehow. This would also explain why the graphing and NOx ppm readings look wrong for the sensors that are showing no errors.

NOTE: I believe the NOx control units have a self-diagnosing function as there are lots of 'NoxSelfDiag' measurement readings in the CR61 ECU data, so they (the two on the CLS) could see the sensors as fine and not report any errors to the CR61 ECU, but the signals from the sensors would be calibrated as per the original sensors fitted and be either higher or lower than expected. These readings may not be part of the NoxSelfDiag software routines, so the NOx control units will not detect anything wrong - I need to dig deeper.

Then: I swapped over the NOx sensors on the control units fitted and took the car for a 15 mile run to get the system active. The MIL illuminated as soon as the system went active and the dreaded Engine start not possible in 500 miles countdown message was also activated. When I got back I connected Xentry and found a fault logged on the rear sensor plus the P13E400 countdown fault. I am still not sure exactly why P13E400 activated, but it's the first time it had and must be related to the AdBlue quality fault - I will look up the detail of why it set later.

Forgetting the NOx Control Unit and NOx Sensor testing for now, I ran all Xentry tests on the AdBlue system, which checked out fine, but soon found that it seemed impossible using Xentry to just delete the P13E400 unless I went on-line for SCN coding with Mercedes, which I don't have access to. However, in short, if you have the correct software and are careful it's possible to: link to the correct ECU in the car; ask it what code it would have sent to Mercedes; put that code into a separate program that knows the Mercedes code generator algorithm and generate the unlock code; and, then send the unlock code to the ECU and unlock it for variant programming. With an unlocked ECU and software that can read and reprogram the ECU it's relatively easy to reset the P13E400 fault code as it can only be active or not, but note there is also a 'tamper' code and a few others settings that need to be looked at as well. You also need to understand that ECUs have different security level codes and how to find what they are and how to select the correct ones etc. - Another detailed subject in its own right.

Anyway, as I sit here writing this, the CLS is sat on the drive with ALL faults cleared, including the P13E400. It's rather cold at present and I don't feel too inclined to do much soon, but I need to evict the cars currently in my garage and get the CLS over the pit. I can then make a few more swaps of NOx Control Unit and NOx Sensor combinations, test runs and then collate and review the data outputs from the CR/61 ECU. I will then dig much deeper into the software I have and see what the Mercedes software engineers built in their NOx routines. Eventually I will have some educated conclusions and detailed documentation for all of this.

Best Regards:

Edward

 

[Richard Moakes]

I don’t do diesel, but I am fascinated by the level of detail you are going into and salute your determination to understand the Nox system.

Please don’t stop Sir, every bit of knowledge gained is valuable.

Richard

 

[EdPhil]

All: Thanks for the thumbs-ups and interest.

Introduction

Since I reset the P13E400 countdown fault, I have only driven the CLS about 58 miles and not had any MIL or NOx fault raised yet. This has involved three ‘drive cycles’ of similar length that each would have been long enough for the NOx system to activate. I currently have a pair of A 000 905 34 03 Q 05 WK9 6681 D control units and new ‘matched manufacturer’ third-party (NS 11A clone) probes that show much higher NOx ppm readings on the rear sensor than the front in Xentry. I am not happy with this and expect errors to occur in the future. I have no further control unit/sensor combinations to try with what I have.

I have not tried two brand new A 000 905 34 03 NOx sensors because they cost over £1K. It would make more sense to have the 'additional installation of special equipment '30o '' service performed and pay for the upgraded sensors, which cost the same and seem to be the proper ‘fix’ for an operational system. However, my interest in the Daimler/Mercedes development software and their test routines has been kindled so I am still having fun looking into what happens at the ECU level when the Xentry buttons are pushed.

Over the past week or so, I spent time scanning through some of the detail I have collected so far (an almost unbelievable amount) and thought I should make a few notes on what my thoughts and conclusions are so far.

Finding easily available, properly detailed and definitive information about exactly what Mercedes/Bosch and Continental have programmed the CLS’s SCR system to do is almost impossible. However, it’s possible to sift through the information I have collected and formulate an educated guess about what has gone on and which advice is most useful.

I must say that some of the most useful information and advice I have obtained has come from site members and Botus in particular.

It would still be great if somebody could supply ‘model’ reference data and graphing under Xentry for a correctly working NOx system, but I have not found or been given anything specific yet. If (or rather when) I get the upgrade I will test it all thoroughly and post the graphing. Recording and backing-up all the data and coding in the car's ECUs as it is now will allow me to compare with the state after upgrade.

Note that I compiled the following details in the next section in advance of posting it here. After reading some info. on another site, I posted it there before this post as I felt it answered some of the queries people there had.

My Thoughts and Conclusions To-Date

I have been trying to understand some logic to NOx sensor problems with my late 2014 CLS for over a year now. I have good garage and tooling facilities, Xentry, Vediamo and Monaco and vast amounts of literature and testing data. I have not finished my deep delving yet or read everything in these posts here, but, noting some of the queries posed, some short details of my conclusions so far might be of use and are thus:

⦁ Selective Catalytic Reduction (SCR) NOx systems were originally designed for big commercial diesel engines that run at relatively constant speeds for long periods. These systems are not really that suitable for people's stop/start cars and the Daimler/Mercedes engineers probably did the best they could to engineer a virtue signalling solution for those pushing it.
⦁ The original sensors fitted to the earlier BlueTEC vehicles did not have to work hard because the system never worked with cleaning NOx as a high priority.
⦁ The original sensors fitted to the earlier BlueTEC vehicles didn't like the Diesel Software Update, which improved NOx cleaning measures but caused them to generate faults/fail.
⦁ If you just replace one sensor or both with new ones they will also generate faults/fail relatively quickly.
⦁ Quick fix 'just wire in a new sensor probe' also looks to fail quickly or not work at all. Third-party sensor probes are lower quality than the original NGK NS11A probes, regardless of what people selling them tell you.
⦁ Mercedes NOx sensors are 'Smart' sensors comprising a Continental control unit and an NGK NS11A probe hard-wired together. Although the Mercedes part number is the same, the control unit can be calibrated differently by Continental and consequently there are likely to be incompatibilities between sensors with different calibrations. Both fitted should have the same calibration number and older ones may 'fail' quicker.
⦁ Most owners, garages and Mercedes dealers don't really understand the Daimler/Mercedes Selective Catalytic Reduction (SCR) NOx system at a very detailed level. It's therefore not surprising that there are many tales of woe with expensive new parts fitted and faults supposedly rectified, but appearing again. - I have been there myself.
⦁ The NOx sensors don't become operational until you have driven for at least 10 miles, and then they quickly go non-operational if idling.
⦁ A lot of the NOx sensor errors are generated after a couple of drive cycles. You therefore may not see any errors after a repair until the vehicle has completed at least a couple of long journeys. If all you do is e.g. commute 10 miles to work and back each day, it's unlikely they will ever become operational and generate a fault until you take a longer journey. - Just hope the ULEZ nutjobs don't cotton on to that!
⦁ It looks like Daimler/Mercedes are well aware of the fact that the Diesel Software Upgrade has caused the hardware problems, but are not publicising it. They have been made to remedy the situation in other countries by regulators, but not in the UK.
⦁ Apart from uninstalling the Diesel Software Update, which is problematic, the only long-term solution appears to be to have the 'additional installation of special equipment '30o '' service performed at a garage (or elsewhere) that has Xentry on-line services. This involves fitting two new NOx sensors and software updates to various ECUs, not just the Engine ECU, and then adaptions to parts of the exhaust system. This is the 'proper' Mercedes fix for NOx sensor problems, but they have not openly told people this.
⦁ Before code '30o', there was a code '121' , but I suspect that the software did not work properly and was therefore quickly superseded. Essentially, the software mod part that affects the NOx sensors is that it changes the speed of readings.
⦁ On a CLS 350 the original NOx sensors (both) number is A 000 905 34 03. The number once '30o' has been performed is A 000 905 35 06. The correct number is only reflected on Mercedes VeDoc and on-line elsewhere after '30o' has been performed. I believe it's the same for all other affected vehicles. The new sensors are the same price as the old ones and at over £1K for a pair it's important not to get the wrong ones ordered/fitted.
⦁ It's worth noting that later production date models (all models of vehicle) had the updated software and NOx sensors factory fitted. Consequently '30o' is not applicable to them. Any CLS where the EPC on-line part number for its VIN appears as A 000 905 35 06 has already been upgraded.
⦁ Many people will be unaware of the proper fix for a working system, although I am aware that there are posts elsewhere that have already said this, albeit with a bit less information as to why.
⦁ I am fairly certain that deleting or 'mapping out' the system is a solution, but illegal. Yes, not buying a BlueTEC as well or dumping it on another mug is another solution. This is about 'fixing' the problem, though.
⦁ Poor and misleading advice far exceeds the good stuff. Search the internet for 'additional installation of special equipment '30o '' and that should provide more authoritative sources of information - not many, but those that count are there.

Regards

Next steps

I will eventually have the 'additional installation of special equipment '30o '' with new A 000 905 35 06 sensors fitted and that should fix it - I trust. The sensors can be a bit problematic to get hold of, but I will probably be seeking quotes in the new year to get it done before spring.

For now, I will just keep resetting any errors I get, and am not too worried about getting any of the restricted miles or starts errors, as I don’t do a lot of miles and can reset even those errors at ECU level. I also have a W212 E class that I rarely have any problems with and that's just sailed through its MOT again - 13 years old now, 60,000 miles and still looks and drives like new.

Best Regards:

Edward

 

[EdPhil]

All:

An error on my E class detail: It's only 12 years old. I got as confused as all the people who don't know the difference between cardinal and ordinal numbering systems and celebrated the end of the millenium a year early!

I did have some additional bits for the last post, but it exceeded the number of characters allowed, so here it is:

SCN Coding of NOx Sensors

From what I have seen so far, I don’t think that the Nox sensor control units get any new coding via Xentry. The SCN coding requirements seem more likely to take the internal serial number and calibration number for entry in Vedoc so the data card records what sensors are physically fitted. I believe Mercedes request a print of the NOx sensor data generated by Xentry during diagnosis and compare that to what's in VeDoc when they get a 'goodwill payment' request from the Merc dealer. If they don't match it's obvious that somebody has swapped sensors and doubt there's any chance of goodwill in such a case. The CR61 ECU itself contains data records about the sensors and notes whether the calibration number is acceptable, but that just appears to update itself quite happily when different NOx Control Units are fitted - if the calibration number is OK it just accepts them. Note that there is also a data segment in the CR61 ECU that states whether or not ‘TT3’ is installed. ‘TT3’ is what the 'additional installation of special equipment '30o '' is about – definitely says not installed in my CLS, but I knew that anyway.

Fault Codes

The first thing that was annoying me about fault codes was that I kept getting codes that were too generic and even Xentry does not explain them properly. I have seen a few offerings of DTC fault code data tables from various people, but almost always found them lacking some specific code I was interested in. Consequently I built some ‘global’ Daimler/Mercedes tables of fault codes for reference – See attached files. Unfortunately, I still have not found the specific code details I was looking for. If anybody knows if the missing ‘sub-type’ code descriptions at the end of that document are available I would be interested in obtaining them.

Unfortunately the main global codes table PDF is about 1200 pages and 26.3Mb normal, 13Mb minimised, so this site's server does not like it. If anybody really wants it I could break it up into smaller files or otherwise? For now, I will do nothing as I think the maximum size is about 4Mb a file and it's pointless for me to spend time splitting it and keep posting things if nobody is really that interested. I don't mind writing these posts if nobody reads them because I keep a copy and they are useful to me.

P13E400 Off-line Code Resetting

For DTC P13E400 resetting information I have attached a 2013 Daimler document (Bosch Reset AdBlue Warning) I came across explaining how to do the reset offline, which I translated and marked-up in English. I then used that in combination with some of the information gleaned from Eastern European and Far Eastern sources to compile a much more comprehensive work specification specifically for my CLS, which has a CR61 ECU – similar to the CR43 example in the document.

The ‘Ecoute’ referred-to in the document is part of the Vediamo software suite. I used that together with a recent CBF file that includes my CLS’s CR61 ECU diagnostic version for the interrogation and reset. A utility called Seedcalc 3 was used to unlock the ECU to the security level needed. I connected from the PC to the car using a SD4 multiplexer. – I would not recommend that anybody tries this if they don’t know what I am talking about. There is definitely 'tamper protection' security on the ECU, which can be reset but you have to be careful. I have also noted 'counters' for fault resets in the ECU that presumably are designed to stop you clearing, e.g. NOx sensor, faults indefinitely. I suspect the counters will activate the limited starts\distance once the maximum value is reached - I need to look at them in more detail.

I am pretty sure that if the whole routine or procedure that xentry uses to effect anything when the buttons are pressed is known, that it would be possible to do anything to the vehicle's systems off-line if you have copies of the flash files for the programming. I believe all Mercedes Flash files were supplied in compressed archives with Xentry until about 2017, but later versions don't have them. Consequently, a lot of the original files for flashing Mercedes ECUs, e.g. pre-2014, are available. Although the newer files can be requested by those authorised to do so for off-line programming, I believe Mercedes expects paperwork justification to release them and that they be destroyed after use. Does everybody comply with that?

Resetting codes and some of the vehicle features is relatively easy off-line. e.g. When I looked at that annoying ECO button which is set to a default of 'ON', it appears that it can be switched 'OFF' (I don't want that) or put into a 'remember last setting' or something similar. I assume that means if you turned it off and then restart the car it will not activate until you press it. I have not tried it yet, but it's on my bucket list.

Up to date CBF files are included with Xentry but I also note that the 'standard' CBF files used in Xentry are 'limited' to a certain extent. Much more detailed ones are available (at a cost) that enable deeper forays into the ECUs. I don't have any of the more detailed ones yet.

Finally for now

I shall be burying my head into the software now and looking deeply at the routines and sub-routines that some of the Daimler/Mercedes engineers have created for SCR.

Happy Christmas to everybody:

Edward

 

[ajlsl600]

Fair play to you bud. A bit over my head short version as I see it nox, adblue poorly thought out and dumped on in suspecting public, only part that seems well thought out is how benz prevent us from fixing it and getting flas files to resolve issues ourselfs
I eagerly await ur further developments which hopefully may lead to an a to z on what to do in event of. And avoid dealer, maker rape 1k+ to resolve an issue they and thier contractors created, after all if prices were peanuts who wud b about with deletes, removals ect the object beind(I thought a cleaner planet, easily achieved by UK laws for makers to provide economic solutions to emissions related pts and software. Instead of the existing cartel and current get around it operators. Given India, Poland, China and Russia among others All pumping out coal, oil pollutants at inconceivable levels one does wonder are we achieving anything other than filling motor makers pockets.

 

[EdPhil]

Ajlsl600:

It’s probably worth stating that I currently don’t believe there is a ‘cheap’ and ‘easy’ ‘quick fix’ solution to get my CLS’s NOx system operating satifactorily. But, that's mainly because its ‘stuck between a rock and a hard place’ with the Diesel Software Update mod installed, but not the ‘30o’.

I suspect that the three ECUs that were affected by the Diesel Software Update could be ‘wiped’ and reset to the original factory settings. The flash files for that appear to be with the archived files that were supplied with the older versions of Xentry. If that was done then the original part number NOx sensors might last a bit longer, but I can’t confirm that I have a decent working pair of them now. New ones for the ‘30o’ update cost the same as the old ones, so it makes more sense to get that update done and fit the new ones.

To do all this interrogation of ECUs etc. I am using software, hardware and other tools that are not necessarily cheap and take some time to learn to use properly. Fortunately(?) for me, I used to do this sort of thing for a living and have the time to do it. I have a broad understanding of most technical disciplines and a very detailed understanding in particular areas, which has taught me that nobody knows everything and most ‘experts’ often are not as ‘expert’ as you or they think. I also know how dangerous a little bit of knowledge can be and that’s why I am looking at a lot of the ECU settings and data, but NOT fiddling with it yet (apart from the P13E400 reset I feel I was forced into). Most people would likely turn their car into a 'brick' if they were let loose on the electronics and it would be a nightmare (and costly) to find out exactly what they had done. Emissions laws can easily be twarted by 'tampering' with the coding so I understand Mercedes tendency to protect their systems. However, I have worked with computers since the 1980s and seen all sorts of hardware and software 'locks' that all fail or get 'cracked' in the end by work-arounds or code-cracking utilities. Consequently there are people who will offer remaps and tools etc. that can be very good, but some can also be very bad and cause future problems.

Most people just want their vehicles to work with all the electronic crap and eco virtual signalling nonsense that makes them feel good. Their minds go into panic mode when they are confronted with detailed technical data and would rather trust others to make it go away. For those people I advise, just get the '30o' update and new sensors fitted by someone with the on-line link to Mercedes and the 'expertise' and 'humility' to know about it and not give you a 'silly' stare when you tell them that's what you want.

Don’t be angry at Daimler/Mercedes in particular. Bullshit and obfuscation is how the world (well the human one) operates. It’s how the powerful elite amass their fortunes. Keep the proletariat’s attention focussed on pretend things that don't really matter, whilst the things that really matter get buggered-up and exploited by the elites with impunity.' Follow the money' is the best advice if you really want to understand the reasons behind world events... Talking of bullshit and obfuscation, if you believe that our governments have saved us all from being addicted to debt and that it's all going to fine, you are in for a nasty shock!

The earth's climate always changes and far more CO2 in the atmosphere than at present is beneficial to that climate for plant life and growing food. As countries (particularly India next), attempt to achieve a 'Western' style standard of living the 'greenhouse' and pollution emissions they generate will far surpass any pathetic little amount 'saved' by the UK. In fact, if the UK and all its population was wiped off the face of the Earth tomorrow it would make hardly any difference to future emissions. Emissions and pollution will continue to rise across the planet for the foreseeable future and all the nonesense that we are being forced to do will have no effect and just make us more impoverished. I would like to believe differently, but having studied it to a very detailed level I have to accept reality.

Wind turbines, solar panels, air source heat pumps and electric vehicles all have their place and uses, but they are never going to satisfactorarily replace all the existing technologies and it's a bit like believing in Santa to think they will.

Anyway, sorry for the rant, but you started it and I agree with you. If stupid and/or corrupt people in power are making-up stupid and corrupt laws that people see are stupid and corrupt it's likely they will be ignored. When too many laws are ignored we enter anarchy, so it's in the law makers interests as well as ours to make laws appear sensible. Outlawing critical thinking so people can't question stupid laws seems to be their current solution.

Santa has attached four PDF files containing the global DTC codes, which I was not going to bother with but, hey, it's nearly Christmas. Together with the two files in the previous post, these give probably the most complete Mercedes DTC listings readily available and should be of use to most people.

Happy Christmas:

Edward

 

[ajlsl600]

Waitin on feryy dieppe newhaven will download that when on home WiFi. But thanks 4 ur efforts I think? I might learn sommat here.

 

[EdPhil]

All:

I was just making a few notes on the other thread on this site where 'Emilys Dad' is being chased to get the Diesel Software Update done to his car and thought I ought to make a few notes here as well to show I have not lost interest yet.

I am still deep into the ECU's programming and also a lot of the Xentry Daimler/Bosch configuration files etc. Lots of detailed information that I am making notes on and may share later. One very interesting detail is that the ECUs have individual DTC tables that are far more detailed than those generally available and displayed in Xentry. I have this table for the CR42, but it's also relevant for other CR ECUs including my CLS's CR61. These codes may contain the same seven characters as the 'normal' ones, but the descriptions are more relevant to the CR ECUs.

I have not had any success with my original aim of just wiring in new probes to the NOx control units and, in short, now believe that's because they are factory calibrated and can't easily be recalibrated 'out in the world'. No binary files appear to exist for direct access to the NOx ECU, and the Xentry Teach-in learns the signal from the ECU and not the sensor like a 'normal' lambda sensor. The NOx ECU is self-diagnosing, so if it is happy with an uncalibrated new probe it does not raise any faults with the CR61 ECU. Consequently, the CR61 only starts complaining about the NOx sensors when the uncalibrated readings are illogical. Hence my CLS telling me there was nothing wrong with the sensors but the graphing results were ridiculous. It also explains why the CR61 thought that the AdBlue quality was poor (it was perfect) because it was probably initiating lots of injection but getting no sensible reduction in NOx values.

So I definitely think that overall the 30o retrofit is the proper fix. However, what I have never tried is fitting two new complete sensors due to cost and all the tales of quick failure. Now that the full ECU and probe Chinese clones are down to around £80 each, I think I will get a couple of those (the pre 30o models) and just see what happens with them before I go for 30o and new model sensors. - update to follow.

Finally, looking at system configuration ini files it seems apparent that the Bosch engineers (they are the actual people behind this) have termed the 30o retrofit as 'TT3' - I don't know what that's short for yet. Apparently, there are 'TT3 fast' and 'TT3 slow' variants, and the part numbers for relevant NOx sensors and Software are all listed. A bit more detail is required to fully understand this.

Best Regards: