Diesel Mass Air flow MAF Temp sensor and power levels
 

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.

Thanks for the info.

Most mafs combine temp and air flow.

What is odd it that the DDE doesnt throw a 'temperature plausibility' fault.... hmmm.

I wonder what the sensor would read open circuit...419 perhaps?

if a new maf fixes it, let us know...

A

Some additional detail:

This particular MAF uses hot film vs hot wire technology.
As ard stated, most MAF sensors also contain a temperature sensor.

I did unplug the sensor and the temperature side still read 419 degrees. This answers ards questions if an open circuit reads 419.

I am very surprised that half the sensor is faulty but we have no indication at all on the dash or display.

Sensor isn't necessarily faulty, sounds like the wiring harness is equally suspect.

What was the final determination for this?
Thanks