In this example, the picture is slightly different:
Here, in the error message data, the engine has worked in Stratified charge (mode 3; required Lambda values 1.99). The binary voltage of the NOx sensor corresponds to the correct indication. Lambda linear of the NOx sensor slightly reduced: 1.49.
Note: after introducing the N43/N53 engines in the production, BMW AG noticed that the piezo injectors’ leaking is quite a common problem. For this reason, in newer SW releases, the manufacturer has reduced the threshold for recording this error message from 1.50 to 1.15. Accordingly, a stronger dripping of the injector is allowed, and it can cause a lower Lambda value of the NOx sensor.
Let’s see the Live data of the fuel mixture:
Control probes report slightly enriched fuel mixture (Lambda slightly <1.00).
And here, the data of the NOx sensor:
As we see, the NOx sensor displays Lambda data appropriate to the situation. Yes, the fuel mixture is slightly rich, but it corresponds to the reported of other probes. I marked the Lambda indications in red because they confirm – one of the injectors is slightly leaking in idle.
At the same time, the Offset value in Overrun mode is increased (16 ppm). In the case of NOXEM, it means:
a. one of the injectors is leaking in a closed position in Overrun mode;
b. NOXEM probe is partially mechanically clogged; it has bad air input.
Regarding the first problem I mentioned in the post above. In this case, the first task is – renew the DME software to avoid the increased sensitivity of the DME to this problem. Of course, it is not a solution to the problem, but the fight with consequences. The updated software will allow the car to work without problems in cases if some injector is leaking only sometimes and slightly.
Next step – replace the injector(s), which is leaking in the closed position.
The cause of the second problem usually is an increased oil consumption (CCV problems or the wear of the engine) or poor quality fuel. Accordingly – the engine oil consumption should be observed; if necessary – the repair works to reduce it should be performed. Fill the fuel only in well-known gas stations.
Note: NOXEM will work correctly also with a partially clogged Lambda probe. But the clogging of the probe indicates some problems in the performance of the engine. These problems should be eliminated to avoid the NOXEM probe (also other elements of the exhaust – Lambda probes, CO, and NOx catalytic converters) problems in the future.