The owner of the car with the N53 series engine approached me. In the DME error message list (in addition to other error messages, including error messages regarding the NOx sensor), the 30E9 also is found. What to do in this situation?
Note: if the error message 30E9 (reduced performance of the NOx catalytic converter) is recorded, two solutions are possible:
a. installation of a new NOx catalytic converter, or
b. NOXEM emulator.
Unfortunately, using OEM (not even talking about China’s “analogs”) NOx sensor in this situation is meaningless. But the owner of the car, obviously, did not believe me, because after some time I received an e-mail from him:
”I had the opportunity to try a new NOx sensor, and regeneration does not work; cold starts go the engine on 5 cylinders…”

Yes, this time, purchasing a new NOx sensor – is a waste of money. There are and can’t be any exceptions. I will shortly explain the algorithms of the DME; possibly, it will refrain you from unnecessary experiments.

During each driving session:
a. DME checks the performance of the NOx sensor. If the NOx sensor is damaged, DME immediately forbids using a Stratified charge. Accordingly – DME switches to limp mode do not measure injectors and do not create adaptation maps of injectors and banks. Vibration, misfires; damages to the CO catalytic converter (during a more extended period) are guaranteed.
If the NOx sensor is in working order (and the engine has no other significant problems), DME:
a. restores Stratified charge;
b. during Stratified charge, measures efficiency of the NOx catalytic converter(s).
In the DME memory, historical data regarding the performance of the NOx catalytic converters are stored. Including – efficiency before and after regeneration; before and after desulfation cycles; time since last regeneration and desulfation, etc. Based on all these data, DME analyzes the performance of the NOx catalytic converter and its reduction.
Suppose DME identified the reduced performance of the NOx catalytic converter, and the profile of the catalytic converter indicates that the situation can be improved by desulfation. In that case, DME tries to activate the desulfation session. If the NOX catalytic converter’s performance did not also improve after desulfation, DME recorded the error message 30E9 in the error message memory.
DME forbids using the Stratified charge when the error message 30E9 is recorded. DME has detected that the catalytic converter is defective, and nothing (except NOXEM) can change this decision. Since this moment, it does not matter whether the NOx sensor is or is not in working order; it reports or does not report data. DME has identified a fundamental l problem. So, in the case of 30E9:
a. the replacement of the NOx sensor with a new/used one will not help (except it is NOXEM);
b. the error message 30E9 can not be deleted., It is always active, and even after deleting it, it immediately “restores” the list.
In the case of the error message 30E9, the only (budget) solution is NOXEM. NOXEM informs DME that the NOx catalytic converter is in good working order, and DME will restore the Stratified charge.
The car owner optimistically tries to install the NOx sensor (it is not even necessary – OEM or China fake). The 30E9 error message (not yet) recorded in the DME error memory is another widespread situation. In this situation, two scenarios are possible:
a. the installed NOx sensor is defective (for a long time, there can be no error messages recorded regarding its performance). DME identifies problems with the NOx sensor. The stratified charge is not used; injectors are not measured. All previous problems continue. Improvements = 0.
b. the installed NOx sensor works correctly. IF the engine has no other issues, DME will try to restore the Stratified charge. From this moment, DME will measure the performance of the NOx catalytic converter. Unfortunately, the E series cars with N43/N53 series engines are 10 years old. With the probability of 99.9%, the NOx catalytic converter has aged. The NOx system does not serve long; that is the harsh reality. Accordingly, with a probability of 99.9%, the error message 30E9 will be recorded, and the installation of the NOx sensor will be in vain.
5 years ago (around the Year 2107), when I developed NOXEM, a small part of these cars with N43/N53 series engines still had the NOx system, which was in working order. Those were the cars which have been maintained very correctly (which means – the NOx sensors have been replaced regularly); they were periodically driving at speed over 110 km/h (desulfation of the NOx sensor was possible), with an ideal driving profile (large distances on highways). Now (2022), the number of performing NOx catalytic converters is almost 0.
Of course, you can hope that, precisely in your case, the situation will be solved by installing the NOx sensor, but – unfortunately, I don’t know any success story.