The specific of N43/N53 series engine – time by time, they NOx catalytic converter has to be cleaned from sulfur. Even the cleanest petrol contains some amount of sulfur, which precipitates on the walls of the catalytic converter and reduces its performance and damages it. These cleaning intervals range from several thousands of km (for new catalytic converter) to 500 .. 1000 km for a used catalytic converter.

If desulphation was not possible by some reason and the catalytic converter is too contaminated, DME records the error message 30EA. The engine doesn’t use Stratified charge, it has problems with creating the adaptations – after a moment, the vibration and misfires start, the staring is difficult. Of course – the fuel cosumption is increased, the exhaust gasses – inappropriate: it’s not possible to pas TI. Some people replace injectors, high-pressure pumps – without success.


Patient: BMW of 1-st series, E81.

Here, the only error message – 30EA. The NOx catalytic converter – contaminated. What to do in this case? With INPA or ISTA D activate the cleaning session of the catalytic converter, drive with speed of 110+km/h for at least half an hour. Paralelly control the temperature of the exhaust (it will increase to 600 oC) and Lambda (it will drop to 0.95).


Said – done. The desulfation session is activated, and we prepare to clean the catalytic converter. Before starting it – one more final test – control of the performance of the NOx sensor.

Not taking into account, that all necessary conditions are reached (the temperature of the engine and exhaust; minimal driving time and speed, etc.), the sensor doesn’t send the data:

Incorrect values are marked with red. They indicate: the sensor has not turned on and is not Online – it is damaged. Unfortunately, this is a very common defect of the sensor. And even more unpleasant – as we see, no error messages are recorded in the DME error message memory. If the sensor is damaged, the engine will not allow the cleaning of the catalytic converter, also Stratified charge is turned off – the engine suffers all problems, which are characteristic to damaged NOx system.


After dismantling the damaged sensor, one more unpleasant surprise follows: the OEM sensor is very old, it has 02 release.

The actual (of last 4 .. 5 years) release is 05. It’s clear – the sensor is at least 7 .. 8 years old. Unfortunately, these sensors don’t serve such long time – it’s clear the sensor was damaged already for a long time – and for a long time the NOx catalytic converter hasn’t been regenerated and cleaned. Accordingly – not taking into account, that the mileage is low, the expensive NOx catalytic converter is damaged for sure.


The owner of the car has two options: replace the complete NOx system (the catalytic converter and the sensor) – costs of repair around EUR 2500, or – to install the NOXEM.

The choice was done in favor of NOXEM.


After installing the NOXEM, certain service procedures have to be performed. In the picture: coding process.


Here, how the NOXEM data in Homogeneous mode look alike: both Lambda data (wideband and narrowband) are reported, also the content of NOx:


Performing the re-adaptation of the engine. First – the flywheel and its sensor:


Then the fuel mixture adaptations for all modes follow. Here, after long years, the engine again performs in fuel-saving Stratified charge mode! Driving with a speed of 100 km/h, fuel consumption: 4,3l/100km!


Here, the NOXEM also confirms Stratified charge with Lambda 2.24!


After a break of several years, the engine renewed the measurements of the injectors. The correction of cylinder No.4 (by placement) is marked with red – the injector is slightly leaking.


And finally – several images regarding the performance of the engine, if it would perform how the manufacturer has intended.

Evenness of the idle in Stratified charge. All bar practically 0!

Such data means – the mechanical efficiency of cylinders is perfectly even! While sitting in the car, we didn’t even felt the engine is running.


Here, the idle in Homogeneous mode – the performance of 4-th cylinder is different (it is increased – the injector injects slightly increased fuel amount) for several % – several days will pass, till DME will completely compensate problem of the leaking injector:

Although this slight difference in efficiency cannot be felt (it seems the engine works perfectly, no vibration), the Siemens management feel and will prevent it! Of course, all this functionality works only in case, if all systems of the engine are in order. Including the NOx system.


After performing the required re-adaptations – short test. All necessary learn bits of adaptations – colored. Adaptations are successfully completed!


The temperature of the engine corresponds to High power mode: LPFP and HPFP pressures – correct, Nernst resistances of both Lambda probes – correct. Everything is in order!

After some time, the “behavior” of the injector No.4 will have to be checked – if its leaking problem will not increase – there is no need to replace it because DME will take in account this difference of parameters and compensate it. If the leaking of the injector will significantly increase – the injector will have to be replaced or cleaned.


P.S. The repair of this engine started with replacement of spark plugs. Cause? The cylinder No.4 stubbornly refused to work, History memory: contained the error messages regarding misfires of all cylinders. The owner admitted, that recently new spark plugs have been installed.

The good ones, not cheap ones are installed. Bosch.

I remind you again: only NGK manufactures the spark plugs for these engines!

Here, in the image – how significantly different are NGK (on the right side) and Bosch (on the left side).