N43/N53 operation modes. Stratified charge performance check

Unfortunately, none of available diagnostic programs don’t give a clear view, in which mode does N43 and N53 performs on current moment AND which modes are allowed. For this reason, we have to use several indirect pieces of evidence and parameters.

First impression – information, in which mode the engine (N43/N53) operates you can find using INPA: system diagnosis/EOL operation mode switching section (../F9/F1)

BMW INPA operation mode menu

Sample: engine operating in Homogeneous fuel mixture mode.


INPA shows, in which mode the engine is operating at the current moment:

a) Homogeneous (from left);

b) Homogeneous lean (Lambda ~1,5);

c) Stratified charge (Lambda 1,8 .. 3,5).

Remark: compulsory switching to Homogeneous and Homogeneous lean mode is possible in idle (Homogeneous lean – if the Stratified charge mode is allowed). If the Stratified charge is allowed, for several MSD80 releases (and specific conditions) it will activate (after pressing F3), if the engine runs on more than 1000 .. 1200 RPM.

BMW INPA operation mode menu

Sample: engine works in Stratified charge with Lambda ~2,0.


First of all: if engine control unit memory contains error messages, which refers to NOx catalytic converter and/or NOx sensor, most advanced modes – Stratified charge and Homogeneous lean – won’t be available. The engine will run in alternative (emergency) operation mode: Homogeneous injection.


Error messages, which don’t allow Stratified charge and Homogeneous lean modes:

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, correlation

30E0 NOx sensor, Offset

30E2 nitric oxide sensor, thrust test

30E4 nitric oxide sensor, aging

30E6 nitric oxide sensor, dynamics

30EA nitric oxide catalytic converter, sulphurized

30E9 nitric oxide catalytic converter, aging


Of course, if there are other (significant) error messages (relating to Lambda sensors, VANOS, etc.) – Stratified charge is not allowed.

If none one previously mentioned error messages are present, you have a hope to see N43/N53 series engine performing as it is supposed to.


To find out, if the engine performs in all modes it is supposed to work:

  1. heat it up to working temperature (95 .. 105 oC);
  2. start the movement with at least 20 km/h;
  3. heat the exhaust system to at least 220 oC;
  4. check, that NOx sensor switches on and start to transmit the data;
  5. continue the movement with speed 70 .. 90 km/h with even speed and load and check, if the engine turns on the Stratified charge mode;
  6. in the Stratified charge mode is on – check the condition (efficiency) of NOx catalytic converter.


And now – how to perform each step:

  1. heat up the engine – I don’t think, that this step requires special instructions. I just want to remark, that don’t do that too aggressive/dynamically – MSD80 can react and turn on the “sports” mode, it means, the Stratified charge will be turned off for a while;

to check the temperature of the engine:

a) open INPA, section MSD80 for N43/53;

b) open the menu for analog modules with F5;

c) open the analog data sub-menu, using F2, then press F6.

2. speed of movement has no limitation – you can drive as slow/fast as necessary, even stop for a while. Main conditions – the exhaust has to be heated up, the temperature of exhaust system reaches 220 oC and speed is more than 20 km/h, at least for some time.

3. to check the temperature of exhaust system:

a) open INPA, section MSD80 for N43/53;

b) open the menu for analog modules with F5;

c) open the NOx sensor sub-menu, using Shift + F2.


On the right corner you can see the indication of exhaust system temperature sensor:


The indicator on the right side shows temperature in Celsius. For NOx sensor to turn on, the temperature has to reach 220 oC and the speed of movement has to be at least 20 km/h.


4. How can we check, if the NOx sensor has turned on and is online? We open sensor’s menu (../F5/Shift+F2, as mentioned before).

On the left side on top you can see the data of NOx concentration:


a) if NOx concentration indication is 0 ppm: then the sensor is turned off, or – if it is on, but (for several reasons) don’t send the data;

b) if NOx concentration indication is different from 0 ppm: the sensor is on and it is sending the actual data.


If the sensor is in working condition, it switches on and starts to transmit data approximately in 2 minutes after necessary conditions are reached:

a) the engine is warmed up;

b) the temperature of the exhaust is at least 220 oC;

c) the speed of the vehicle is at least 20km/h.


Unfortunately even in this stages “surprises” can happen. NOx sensors are supplied by Continental, which already has changed several generations and even more software releases, nevertheless ALL tested software releases had one feature in common: when the sensor ages (above 50’000 .. 80’000 km), it has troubles to switch on and start “working mode”. There is a technical problem – reaction time increase and never-ending current oscillation in cameras of the chemical sensor (oxygen and NOx), as a result of this – control system for Electronics cannot reach stable working condition. Typically, in this situation the sensor try to switch on (starts the heating of the sensor) and sends “not ready” status to MSD80; MSD80 does not register any error messages, it simply waits for the sensor to start to perform – waits for a long, long period of time.

In case you have the described situation (NOx indicator continues to display NOx value 0 ppm for a long time, the same time exhaust temperature values are changing, it means: INPA is connected to MSD80) – the NOx sensor has to be replaced: it’s damaged.

if the NOx sensor starts to transmit the actual data (NOx values differ from 0), it’s time to check, if Stratified charge mode switches on – the most important and also most complicated operation mode of N43/N53.


The Stratified charge can be seen in two menus:

a) exhaust (adaptations) menu – /F5/F6;

b) NOx sensor menu – /F5/Shift + F2.

In both menus you have to check Lambda values; exhaust menu – values for wide-band Lambda for both banks (before catalytic converter); NOx sensor menu – sensor’s reported wide-band Lambda value (second line on the right side in menu).

NOx sensor menu:


Exhaust menu (adaptations):

BMW INPA adaptations menu

5. Accelerate to 70 .. 90 km/h, switch the cruise control on and follow the Lambda values.


In few minutes (if the engine has no error messages – almost immediately) Lambda value has to reach above 1,4.

If the Lambda value stubbornly stays around 1,0:

a) it is possible, that before there was a very dynamic driving, MSD80 has switched off the Stratified charge mode. If yes, stop for 2 .. 3 minutes, accelerate (normally) to 70 .. 90 km/h and continue to observe Lambda values;

If the Lambda value stays approximately 1,4 .. 1,6:

b) control unit has observed real (you can not miss the signs – you will feel twitching) or fake (description here) uneven running on Stratified charge mode and/or insufficient efficiency of CO converters and (very soon) you are supposed to see the corresponding error message:


3104 uneven running, stratified charge operation

or error messages:

29F4; 29F5; 2A26; 2A27 relating to CO converters, more information here.


In this case, the cause of uneven running has to be averted – but only in case, if you really feel the twitching of engine. If there is no real problem (no twitching etc.), the cause of this error message can be an uneven road, as described here.

c) high NOx values. If the content of NOx in exhaust has reached several hundred ppm already from the start of driving – it look’s that there is a problem. If there are no error messages regarding NOx catalytic converter:


30E9 nitric oxide catalytic converter, aging


there is a high possibility, that this error message will soon appear or is “masked”: tuners deleted it from MSD80 error message map. Yes, there is no error message, but engine doesn’t perform a it supposed to. In this case, you have to check software release in MSD80, if it don’t comply with one offered by producer – it has to be restored. The existing (most probably – tuned) version can be stored as copy and restore it’s function when the engine problems will be solved.


If the engine has no operational problems, Lambda has to reach over 2,2.

If by speed 70 .. 90 km/h Lambda reaches 2,6 .. 3,2 – congratulations! The engine performs in Stratified charge mode! If Lambda reaches 1,4 .. 1,6 only – (as described before) the Stratified charge mode is allowed, but the control unit has detected some kind of unevenness (could be misfire in any of cylinders), or NOx catalytic converter performance is reduced, and the engine has switched to Homogeneous lean charge mode (the performance of this engine mode is widened (for a while) to area of middle loads).

Reducing of Lambda, if the reason is real (not falsely detected) misfires (for a while, after some  moments MSD80 will try to increase Lambda to max 2,6 .. 3,2) it’s not a critical error, but it should be solved – an excess of fuel in exhaust system damages the catalytic converters.


If the Lambda reaches 2,6 .. 3,2 – let’s move to the last stage of this test: evaluation of catalytic converters performance.


6. Evaluation of NOx catalytic converter performance.

In this test, you have to use a chronometer to record, for how long time Lambda is above 1,4. After some time (10 .. 60 seconds) Lambda (for several seconds) will decrease below 1,0 – in this period of time MDS80 will perform the regeneration (cleaning) of NOx catalytic converter. Several consecutive cycles have to be measured, the longest of them has to be considered as a result.

When several cycles (at least 3) of Stratified charge are measured, the longest of the chosen as a result, we can evaluate the condition of NOx catalytic converter:

a) 30 .. 60 seconds. Unbelievably perfect result. If the NOx catalytic converter has not been “freshly”   (during last 10’000 .. 20’000 km) replaced – such result is not possible;

b) 20 .. 30 seconds. Congratulations! The NOx catalytic converter is in working condition. For future you have to use high-quality low sulfur fuel, follow up all the systems of the engine, and you will enjoy all drive of N43/N53 for a time;

c) 10 .. 15 seconds. 10 .. 15 seconds is a minimum time for Stratified charge cycle. 10 .. 15 seconds mean: NOx catalytic converter can not handle the accumulation of nitrites. If error message 30E9 is not present yet – soon you will see it. You can try to perform forced regeneration of catalytic converter, using ISTA D service functions, but don’t be too optimistic, that it will improve the situation.

Note: if you notice shorter Stratified charge cycles (between longer ones), or even longer periods (till one minute) the Lambda is 1,0 – no need to worry. MSD80 regularly performs the calibration of wide-band probes for each bank, it calibrates also Lambda values for NOx sensor, calibrates reference level of NOx sensor, performs individual Lambda corrections for each cylinder and each bank. In moments of calibration lambda varies from 0,97 .. 1,03. MSD80 performs also regular check-up of EGR and other systems – also in those moments Stratified charge is stopped for a while.


Related entries:

Rough run. Trim errors. Hidden cause

N43/N53 operation modes. Basics

Performance check of NOx sensor

Direct injection. Stratified charge

NOx catalytic converter regeneration and desulfation

FAQ about NOx emulator