It is not a secret to anybody that I am working on the NOx topic. It is not a secret to entrepreneurs from China.

Already 5 years ago, some sellers from China got in touch with me to inform me that China has “developed” their own NOx sensor, and they are ready to offer it as an analog of the ones manufactured by VDO. Over time it became clear which is the “scientific institute”, which has “developed” (actually – tried to copy the original) sensor, and who is the manufacturer who produces electronics for these sensors. 

For several years, the re-sellers offered to purchase these sensors. They said they could adjust the inscriptions in the way I wanted them. Say, if necessary – let’s make them max similar to the original. True, thou, some 100 pieces or more should be purchased. The manufacturer also offered a non-free-of-charge sample, but when I did not show any interest, the right moment came! I got an offer, which I could not decline. Chinese offered a free sample! Isn’t an excellent offer?

Today I received the sample. Such sensors can be purchased via AliExpress for some EUR 100 .. 150. You can purchase them for a higher price, too: from Metzger, VEMO, etc. (more information here and here).

I already prepared an impressive test program, but… Almost all of it failed. But now, about everything in turn. 

I received a sample with its “default” look. On the label, a partial BMW code (last seven digits) and also the nomenclature marking of VDO can be seen. 

Here I would like to make the first remark: do you see the digit 03 after the last symbol 129 of the code? 03 means the version of the release. The up-to-date release is 05, and it has been in production since the Year 2010 .. 2011. Conclusion – the sample for copying was a sensor, approximately 12 years old. 

Does it change anything? Of course, it does – newer versions have updated both in hardware and software. 

I connected the sensor to the test equipment. 

We already see the first potential problem. One of the inputs of the OEM sensor is used to detect where the sensor is located: before or after the NOx catalytic converter. It allows one to connect two identical NOx sensors to the same CAN bus (it is necessary, for example, for all BMW diesel cars, which have the AdBlue system). Unfortunately, this feature does not work at all on this sample sensor! Due to this problem, part of these sensors (depending on the connection schematics, TIS should be checked for details) will not be recognized at all! DME will immediately record the error message regarding non-existent data. And, to make the situation even more “fun,” such a sensor will paralyze the work of the second NOx sensor (if such is installed), and there will be error messages regarding it too! So – you will install a new (and as if working) sensor instead of the old/damaged one, and as a result – DME will have error messages regarding both sensors, and the performance of the engine will be completely incorrect (even till the stage, that it will not be possible even to start the diesel engine)!

The second nuance, which I noticed immediately – the temperature of the exhaust gases, reported by the sensor in the room temperature, is incorrect. The error is around 50oC; the curve of the reported temperature does not correspond to the actual temperature. What troubles can this problem cause?

Due to the incorrect temperature reported by the NOx sensor, the temperature sensor of the exhaust gases will be trimmed incorrectly. DME can record the error messages regarding this temperature sensor. Needless to say – replacing the temperature sensor will not help because it is not the actual culprit. Even if the DME does not record the error message due to incorrect trimming, the exhaust temperature in specific performance modes will be incorrect, for example, during desulfation. During desulfation, DME maintains an exhaust temperature of 600oC and stabilizes it using the temperature sensor’s readings. But, if this sensor is trimmed incorrectly, the exhaust temperature will be incorrect too. If it is much higher, all exhaust elements (CO catalytic converters, probes, NOx catalytic converters, too) can be damaged. The car even can start to burn!

After turning on the sensor, the test of the sensor management and its performance was on my checklist. 

I gave the sensor command to warm up its probe, switch to the Online mode, and report the status. The reaction of the sensor – NONE. I sent the command once again – no success! The sensor is “deaf”!

I checked other commands: sent ID data, sent self-test report status, and others. ZERO reaction! 

Would my equipment be damaged? I connected the OEM sensor; then connected NOXEM – they all “talked” and performed the commands. So – everything is fine with the equipment! 

Without any slightest doubt – the Chinese “specialists” haven’t even noticed that these sensors require two-way communication! They haven’t implemented receiving and sending of the commands!

What are the consequences of ignoring such basic functionality?

First – regular error messages regarding the inappropriate versions of the sensor. This is nothing new, and I have seen it quite often. If the sensor does not report its ID data (when they are required), DME decides that the sensor is “alien” and ignores it from now on. 

Second – if the sensor does not understand the command to start the gas analyzing task, it stays in Offline mode and does not send data! This is also a quite common defect. Instead, if the sensor decides by himself when to switch to Online mode or perform any other task – the error messages regarding data mismatch, status, and Lambda parameters are guaranteed! 

Unfortunately, my tests were done even not started. It DOESN’T MATTER at all if the “head” of the sensor “knows” the content of the NOx and how long it would perform – if the communication of the sensor with DME is incorrect, all this is hopeless. Yes, BMW has created a complicated communication format with the NOx sensors. And it is exactly to make the forging of the sensors as complicated as possible. But – who said that it would be easy? 

The integrity of NOx data was left out. Lambda Linear and Lambda Binar data plausibility and precision tests were left out. Sensor status, error messages, and self-test data checks were left out. So much could be tested and evaluated. At the same time – it does not make any sense anymore… 

For example, to others, “more simple” brands, it is skipped – they have no measuring of the exhaust temperature and no two-way data communication. But – not for BWM. Yes, Chinese “specialists” haven’t managed BMW. 

My conclusion – it does not make sense to install these sensors, regardless of price! Communication with DME is organized entirely wrong, and these sensors DO NOT WORK! 

p.s. and again, the remark: if the NOx catalytic converter of the vehicles is damaged (well, now in the Year 2023, we can say – practically all E series and F series cars with N43/N53 engines), it makes NO sense to install the OEM sensor. OEM sensor will report the increased nitrite level in the exhaust to the DME, and… DME will forbid the use of Stratified charge. In this case, the only solution is NOXEM.