Replacing NOx sensor for N43/N53

When fuel consumption grows, most probably, the rough run of the engine has also started

BMW NOx sensor

If MSD80 has registered following error messages (one or few of them):

2AEC Nitrogen Oxide Sensor Self Diagnostics

2AF0; 2B05 nitric oxide sensor, heating

2AF2; 2B06; 2B09 nitric oxide sensor, Lambda linear

2AF4; 2B07; 2B0A NOx sensor, electrical

2AF6; 2AFB; 2B0B nitric oxide sensor, Lambda binary

2AF9 nox sensor, nox signal: coast mode check

2EAE NOx sensor message missing (timeout)

30D6 nitric oxide sensor, plausibility

30D8 NOx sensor, Sensor damaged

30DA NOx sensor, heating time

30DC nitric oxide senor, heating

30DE NOx sensor – Lambdaprobe before catalyst, Korrelation

30E0 NOx sensor, Offset

30E2 nitric oxide sensor, thrust test

30E4 nitric oxide sensor, aging

30E6 nitric oxide sensor, dynamics


but DON’T contains:

30E9 nitric oxide catalytic converter, aging;

30EA DeNox catalytic converter sulfurized;


there is a hope, that just change of NOx sensor could help. The number of recorded error messages is not important, usually, they are in groups, because, for example, Lambda binary is mathematically calculated from Lambda linear, and if the probe is “dead”, both values are not legit; and additionally also error messages regarding plausibility, correlation etc. are present. Detailed description how to check the performance of NOx sensor, read here.

If you see any of these error messages:

  1. 30E9 nitric oxide catalytic converter, aging;
  2. 30EA DeNox catalytic converter sulfurized*;

*Note: check also Info list ../F4/F2/F1


it won’t be so easy, unfortunately…

Note: sometimes no errors are recorded in error message memory. Read how to perform functionality test of NOx sensor.

Attention! The average lifetime of expensive NOx catalytic converter is around 150.000km. If the NOx sensor is damaged, the engine management system MSD80 cannot determine the remaining capacity of NOx catalytic converter and error message 30E9 about the aging of NOx converter will NOT be stored even in a situation if NOx catalytic converter is damaged. This message (and all consequences – increased fuel consumption, rough run, misfires) may appear after replacement of NOx sensor (if brand new OEM sensor will be installed). If mileage on your car exceeds 150.000km we recommend using NOXEM even if the 30E9 error is not stored. NOXEM will restore full performance of your car’s engine even if NOx catalytic converter is aged, damaged or removed.

Scenario 1: there are only error messages regarding NOx sensor, error messages 30E9 and/or 30EA are not present.

Changing the sensor:

  1. physical replacement;
  2. deleting the long-term trims/adaptations (offset values for Lambda and NOx data, etc.) of the sensor with ISTA D (procedure of encoding of new NOx sensor, described here).

Deleting/clearing the adaptations of NOx sensor is a very important event. If they are not cleared, there can be scenario that MSD80 identifies seemingly high value of NOx level after regeneration cycles and registers error message 30EA (MSD80 is supposed to initialize forced desulfation of NOx catalytic converter to clean it) or even 30E9 (aging of NOx catalytic converter) after some time (if desulfation sessions are not successful or possible). Also error messages 30D6, 30DE, etc. can appear.

Additionally: if the engine memory has recorded any error messages regarding fuel trim, misfires, Lambda probes, CO catalytic converters (more detailed description here: the Hidden cause of rough run), the long-term fuel trims has to be deleted! Why?

  • if the Stratified charge was lost, the reference values for others engine modes, the engine itself has “flown away”, and it is not able to keep the fuel mixtures as needed;
  • only after deleting old long-term fuel trims, MSD80 will start to correctly create new ones. More about this issue read here.

Of course, all error messages also have to be deleted now.

Then you can perform the long-term trims.
How to do that – you will find here:  How to create adaptations


Scenario 2: if the error message 30EA is present.

After replacement and encoding of new NOx sensor (if there are error messages regarding NOx sensor), or, if the error messages regarding NOx sensors were not present – we continue from this place:

  1. with service functions of ISTA D choose regeneration of NOx catalytic converter, follow the instructions;
  2. fill the fuel tank at least till half;
  3. at least for half an hour drive with speed 110 km/h or faster, control the temperature of the exhaust system (should be at least 600 oC) and status of NOx catalytic converter sulphation (should decrease) using ISTA D or INPA.

If the catalytic converter has only sulfur “poisoning” – this will help.

INPA  ../F9/Shift + F3/F1. NOx catalytic converter poisoning level.


After this:

a) clear error memory;

b) delete all fuel adaptations;

c) create new adaptations (as described here).


Continue to use only high quality fuel!

More about management of NOx catalytic converter


Scenario 3: if the error message 30E9 is present.
The hope, that something can be done easily, is very little.

What can be done:

  1. if there were error messages regarding NOx sensor – you can hope, that error messages are because of faulty NOx data it is considered “dead”. Then you have to replace the NOx sensor, reset it’s long-term trim data (as described above);
  2. perform the catalytic converter regeneration program, if possible;
  3. perform the encoding of new catalytic converter’s registration, using ISTA D (in the same service section, where regeneration).

When “new” catalytic converter is registered, the engine will try to perform the Stratified charge. If no other error messages are present, it’s worth to perform this: Performance check of Stratified charge, and after “evaluate” the NOx catalytic converter’s work-ability. Sometimes wonders happen – and maybe you will be the lucky one.

A fundamental solution of problem described above – NOXEM series NOx emulator.  If OEM NOx sensor is replaced with NOXEM, you can enjoy all benefits of N43/N53 engine (Stratified charge – lower fuel consumption) and smooth run regardless of condition of expensive NOx catalytic converter.

Detailed information about NOXEM 129

Detailed information about NOXEM 130


P.S. It’s not possible to delete error messages 30EA and 30E9 easy way (for example, delete and – problem solved). 30E9 will re-appear in a little while, the status of 30EA is saved and visible in INPA info and/or history menu section. If the 30E9 was present – to renew Stratified charge mode, you will have to perform (successfully) operation described above or install (and register) a brand new catalytic converter (if you don’t mind spending EUR 3000 on that).

P.P.S. As already mentioned in other topics, the problem of faulty NOx catalytic converter can’t be solved deleting it from MSD80 error map (by modifying it), and disconnecting of NOx sensor won’t help also.


Note 1: when adaptations are cleared, following error messages* can appear immediately:

  • error messages relating DSC. Solution: drive 10 .. 15 min, switch off ignition for 2 .. 3 min, then turn on;
  • error messages relating throttle. Solution: turn on the ignition, press and release accelerator pedal for 3 times, then start the engine.

Note 2: during adaptation process (after old adaptations have been cleared) some error messages* can appear:

  • error messages relating fuel trim (bank and/or cylinders individually);
  • insufficient performance of CO catalytic converters;
  • Lambda probes (trim and/or signal);
  • uneven run (Stratified charge and/or Homogeneous injection).

*these error messages in the exact situation do not indicate any problems with the engine performance.


After new adaptations are completed (after 5 .. 8 driving sessions for cold/warm engine, at least 200 .. 300 km), check the new adaptations and clear error message memory using INPA or ISTA D, if necessary.


Related entries:

Performance check of NOx sensor

Encoding of new NOx sensor

Encoding of new NOx catalytic converter

Components of NOx system

NOx sensors. OEM codes

30EA. NOx catalytic converter sulfurized

30E9 nitric oxide catalytic converter, aging