Diesel Mass Air flow MAF Temp sensor and power levels

[F1Stix]

Today I discovered the MAF sensor is a combination of air intake temperature and mass air flow. On the X5 if the intake air temperature side of the sensor is faulted or bad, there will not be a service engine soon light. If the MAF side of the sensor fails, you will get a "service engine soon and reduced power" indicators on the display.

If you have noticed reduced power or poor fuel economy, a quick check with a scanner that can display the air intake temperature values will show you if it is operating and indicating to the ECM properly. My sensor was reading at 419 degrees. Most likely this is the outside high range of the sensor and it has totally failed.

Looking back at the old data scans, the usual range is 99-110 degrees when the engine is warmed up.