Stratified charge. Disabled?

Several readers of my blog have asked: why does the engine of my car don’t runs in Stratified charge?

Of course, if the DME error message memory contains the error messages, which are related to its basic systems, including NOx system – the Stratified charge will not be turned on. Let’s talk about situations when the error list is empty and everything seems to be ok.

Unfortunately, the engine doesn’t perform Stratified charge. Why?


Possible reasons:

1. Hidden error message 30EA (NOx catalytic converter contaminated with sulfur). If this error message is deleted, but the desulfation of the NOx catalytic converters is not performed, it will not appear in the error message list, but the status of increased contamination of the NOx catalytic converter remains. The solution: evaluate the contamination of the NOx catalytic converter (../F9/Shift+F3/F1) and, if necessary, perform the desulfation session. Before deleting this error message, always clean the NOx catalytic converter.

a) If the car has OEM NOx sensor installed, the desulfation session has to be done if the contamination of the NOx catalytic converter overreaches 600 .. 1000 mg.

Note: if the error message 30EA has been observed already before, if the mileage of the car is above 100.000 km, if the car has been used with a damaged NOx sensor; the driving profile contains a low driving speed (city mode) – perform desulfation already by contamination level of 400 .. 600 mg.

b) If the NOXEM is installed, the desulfation session has to be performed, if the contamination of the NOx catalytic converter overreaches 3000 mg. An alternative solution in case of NOXEM: encode the replacement of the NOx catalytic converter, using ISTA D/+.


2. Hidden defect of the OEM NOx sensor. The following defect of the OEM NOx sensor is very common: the sensor is not able to complete a self-calibrating process. At the same time, it doesn’t send any error messages, also DME doesn’t see anything suspicious in the performance of the sensor, because it endlessly “prepares” for the work. Seeing, that the sensor after a certain time (after receiving a command to start heating of the sensor and sending life data) is still not Online, DME stops Stratified charge till the moment, when the sensor will be Online. To make sure, that the sensor is not one to blame, you have to check, if it sends Online data (../F5/Shift+F2/F1), the content of NOx should be different from 0 ppm (conditions: the engine is warmed up; the temperature of the exhaust reached 220 oC; driving speed at least 20 km/h for at least 2 min).

Note: this problem is not actual for NOXEM.


3. If the car has OEM NOx sensor installed: DME has detected the reduced performance of the NOx catalytic converter. There could be several reasons (additionally to wear or damage to the catalytic converter) for such situation, for example: low-quality fuel (with a high content of the sulfur), decreased exhaust temperature (for example, the car has driven into a deep puddle or snow-drift), etc. DME will restore Stratified charge after a certain time and will repeatedly evaluate the performance of the NOx catalytic converter. If several such attempts to restore the Stratified charge will confirm, that the problem doesn’t disappear – obviously, the NOx catalytic converter, however, is damaged. DME will inform you about this fact by recording the error message 30E9. But it will take some time until this error message will be recorded – during that time DME will step by step turn off the Stratified charge in conditions when the NOx emissions are most high (for example, driving the highway with speed 100 ..130 km/h).

Note: in case of NOXEM installation this problem is not actual/possible.


4. DME has detected short-term (or permanent) reduce of performance of the CO catalytic converter in Stratified charge mode. After a certain time, DME will restore Stratified charge and will perform repeated measurements of the performance of the Stratified charge. If the problem will persist longer than acceptable, DME will record the error messages 2A26 and/or 2A27 in the error message memory. But, the same as with the NOx catalytic converter, also the measurements of CO catalytic converters take quite a lot of time (DME don’t record the error messages regarding catalytic converters immediately, to avoid false alarms).

Note: performance of the catalytic converters could be reduced due to increased oil consumption (typically: in case of CCV damage), leaking injectors, incorrect adaptations.


5. The engine prepares for a desulfation session. In this case, when increasing the driving speed above 70 .. 90 km/h. DME will switch the engine to Homogeneous mode, the econometer will indicate increased fuel consumption (+1 .. 2 l/100 km, even comparing to “normal” Homogeneous mode), the exhaust temperature (../F9/Shift+F3/F1) will increase above 350 .. 400 oC (reaching 600 oC). If you will drive with speed high enough to start the desulfation session when the temperature of the exhaust will reach 600 oC, Lambda of both banks will reduce to 0.95 and the NOx catalytic converter will clean itself slowly. If the driving speed will be insufficient, after several minutes of trying the desulfation session attempt will be postponed for a moment. But, as soon as DME will identify “hopeful” conditions for desulfation, it will immediately restore the preparation to this procedure. In addition, the amount of contamination of the NOx catalytic converter (../F9/Shift+F3/F1) doesn’t describe precisely the conditions, by which the DME will start the desulfation. The approximate indications are the following:

a) if the car has OEM NOx sensor installed, even in case of a perfectly working system the critical (last) moment of desulfation is around 1000 .. 1500 mg, for typical (10 years old) NOx system the critical threshold is 500 .. 700 mg;

b) if the car has NOXEM installed, the critical level of contamination is 3000 .. 3500 mg, but, if the car regularly drives 110+km/h, the desulfation session can be activated also after reaching 1500 .. 2000 mg (because the DME don’t know if at the next stage its owner will drive with speed necessary for desulfation system, so by “safety reasons” the desulfation session will be done very timely, long time before reaching the critical level of contamination).


6. DME has identified the uneven performance of the engine and has switched off the Stratified charge for some time. It should be noted here, that in such situation the switching-off of Stratified charge is done in several steps. At the first stage, DME switched the engine in Homogeneous lean mode, with Lambda around 1.5. If also in this mode the performance is still uneven, the engine is switched to Homogeneous mode. So – you would have to feel the unevenness in the performance of the engine. Second – after a certain time (or more) the error message 3104 have to be recorded (with active status).


7. It is possible, that the DME performs some of the service procedures. The list of these procedures is quite long: for example, the airtightness test of fuel tank valve and system and adaptation of the valve; adaptation of throttle; check-up of the EGR system and adaptation of valve; adaptation of the wideband probe(s); the performance tests of the CO catalytic converters in Homogeneous mode; common test of the fuel mixture for banks in Homogeneous mode, etc. As more frequent service procedures are performance tests of injectors (flowrate, leaking, atomization quality). When performing these tests, DME tests the “behavior” by different opening times, changing the proportion and moment of injection of the impulse of injection (they are 2 or 3, depending on driving mode).

All procedures, mentioned above, are performed:

a) in a routine order (or after a certain time);

b) out of order – if DME detects any problem (for example, the uneven performance of the engine, misfires, high integrator’s values or inappropriate Lambda; increased, reduced amount of consumed fuel; inappropriate air mass or similar).

What we – users of this complicated system – can do? At first – check learnbits: ../F5/Shift+F6/F2

If you see such “picture” – DME has successfully finished all injector adaptations (and tests). Also, if the learnbit of 1-st column 2-nd row is not colored (it refers to additional adaptations of engine banks by lowered temperatures) – there is no reason to worry: this learnbit doesn’t turn off Stratified charge. But, if the learnbit of a 2-nd column/4-th line is not colored, or/and any learnbit of the 3-rd line is colored – at this moment DME performs service of procedure of measuring the injectors.

What to do in this situation? There is no reason to worry. When driving evenly, DME will measure all parameters of injectors and will restore Stratified charge. If DME will see, that even driving mode is not possible (the engine work mode will change regularly), after a certain time this service procedure will be postponed.

In any case – after a certain time the Stratified charge will be restored. How much time (patience) it will cost? The answer to this question is known only to the software developing team. We – users of the system – just can be patient.


8. If Stratified charge didn’t re-appear after adaptations were cleared using ISTA D/+

a) check flywheel learnbit at ../F5/F7 using INPA; if the learnbit is not colored – let the engine in the overrun mode for at least 5 seconds (drive with at least 100..110km/h, select 4th gear and release accelerator pedal) several times until learnbit becomes colored. Restart the engine;

b) check the heating status of Lambda probes at ../F5/F6 (first two lines). If probes are not heated (heating values less than 30%), let DME to the sleep mode (switch of ignition and wait till backlit of Start/Stop button is disabled), then start the engine again. If the problem still persists – check injector’s coding data. Recode injectors using ISTA D/+.


At the and I would like to remark: N43/N53 series engines are designed for long distances and high average speeds. Exactly by this reason, they are so economical, but at the same time: complicated, expensive in production end exploitation. If driving long distances on the highway, all service procedures and cleaning of NOx catalytic converter will be done quickly and without a hitch. If the car is used only in a city mode, both successful finish of the service procedures and timely desulfation of the NOx catalytic converter are done. Self-evident – both problems reduce the time of using of Stratified charge.