NOx sensors could be (and very often are) the reason, why the engines of the N53B30 engine family do not use a Stratified charge. Very often the error messages regarding these sensors are not recorded in the error message memory of DME even in cases of fundamental damage. Unfortunately, the diagnostics of the NOx sensors for F series vehicles (N53B30 petrol engine family) with the diagnostics equipment is very difficult. BMW has denied access to any pe of data, which corresponds to the NOx sensor.

These sensors have several hidden defects (detailed information read here), regarding which the error messages in the DME error message memory are not recorded, but the performance of the engine is impaired, Stratified charge – turned off. Some of them:

• problems with finishing the self-test/calibration. The sensor does not switch in Online mode and does not send live data;
• incorrect offset of NOx data. The sensor sends an increased amount of NOx and misleads DME regarding contamination and damage of the NOx converter;
• incorrect measurements of the exhaust temperature. The sensor misleads DME regarding the lowered temperature of the exhaust, DME does not switch the sensor in Online mode and does not use a Stratified charge.

Bimmerprofs offers diagnostics of the NOx sensors for the F series. During diagnostics, more than 17 parameters of the NOx sensor – static and live values, are inspected.
After diagnostics, you will receive the report regarding the performance of the NOx sensor.

Disclaimer. Very often the defects of the NOx sensor are sporadic. Performing a sensor performance check, the sensor will be tested for 15 minutes, turning it on and off for at least 5 times – it will be subjected to the thermal stress to make the detection of the defects easier. If the sensor will not indicate the required performance for even one time, these problems will be noted in the Diagnostics protocol. Unfortunately, even such a scrupulous diagnostics does not exclude rare cases, when the sensor is not able to switch in the Online mode or indicates other defects. Therefore, if the test result in the diagnostics protocol is marked as “suspicious”, we recommend replacing the sensor.