One more example of the error message 30DE. As usual, we start with freeze-frame of the Error message:
As we see, Lambda, required by the DME, for both banks was around 1.50. Homogeneous lean mode? At the same time, the car was driving at a consistent speed of 130 km/h. At this speed, the N53 series engine should work in Stratified charge mode!
What forces DME to switch from Stratified charge mode to Homogeneous lean mode? Misfires!
Here, the fuel mixture data!
Not taking into account a correct Lambda 1.00 at the 2-nd bank (additionally, the CO catalytic converters are warmed up), the control probe confirms the presence of oxygen in the exhaust. The direct confirmation of the misfires!
If there are misfires in any of the cylinders, a range of problems appear:
a) the control probes continue to report the oxygen in the exhaust; DME incorrectly trims the wideband probes. Strongly enriched fuel mixture is supplied to the cylinders;
b) unburned fuel (due to enriched fuel mixture and misfires – both problems are summing up) gets in the exhaust and overloads the CO catalytic converters; poisons the Lambda probes and the NOx sensors, and it also can create a blast, which can eradicate the probes.
Data of the NOx sensor:
This time also, the NOx sensor indicates correct data when data are fetched. According to the data of the error message, the probe of the sensor was poisoned with the fuel when the error message was recorded (the value of Lambda linear was increased).
The main repair in this example – fix the misfires. The problem is compounded by the fact that no misfire data are available via the EDIABAS. You will have to find an ELM 327 adapter and the appropriate software, which can “see” OBD Mode 6. On the other hand – thank you to BMW AG, because, for example, for N52 series (and older) engines, the misfire counters are not available at all.
After eliminating the misfires’ cause, make sure that the DME restores Stratified charge in all driving segments, and the misfire counters for all cylinders after longer driving sessions are close to 0. Only then can you consider that the repair was successful.
Do not postpone the repair! The fuel, which gets in the exhaust, gives permanent harm to the NOx and CO catalytic converter and all probes, controlling the content of the exhaust gases.