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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > MAF / INPA Help



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      03-30-2020, 04:15 PM   #1
meikster
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MAF / INPA Help

Hi guys, just looking at the raw values portion under live data, i noticed my hfm sensor air mass was 0v and 0.0 kg/h, is this pointing to defective maf sensor or possibly poor wiring? Luftmasse under mwb1 shows 12kg/h at idle, are these 2 numbers normal? Any help greatly appreciated!
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      03-30-2020, 04:49 PM   #2
nsjames
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it's possible that your model simply doesn't use that sensor.

sometimes inpa gives out readouts for things that don't exist on your car.
can guarantee that if your MAF sensor was reading 0 there would be a SES light on. Because I've forgotten to plug it in before, and it instantly sets a light.
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      03-30-2020, 05:52 PM   #3
meikster
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Quote:
Originally Posted by nsjames View Post
it's possible that your model simply doesn't use that sensor.

sometimes inpa gives out readouts for things that don't exist on your car.
can guarantee that if your MAF sensor was reading 0 there would be a SES light on. Because I've forgotten to plug it in before, and it instantly sets a light.
appreciate the response, I kind of figured the same as I unplugged it and did give me a CEL.
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      03-30-2020, 10:34 PM   #4
gbalthrop
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Quote:
Originally Posted by meikster View Post
Hi guys, just looking at the raw values portion under live data, i noticed my hfm sensor air mass was 0v and 0.0 kg/h, is this pointing to defective maf sensor or possibly poor wiring? Luftmasse under mwb1 shows 12kg/h at idle, are these 2 numbers normal? Any help greatly appreciated!
Your car is fine. Your INPA installation is fine. It's a matter of Analog vs. Digital.

MAF Sensors (non-turbo engines) PRIOR to 2007 models were Analog and produced a varying voltage. Effective 9/1/2006 for 2007 Models (N52KP engine), the MAF Sensor is Digital, and sends a "Duty Cycle" or PWM signal. So your Messwerte 1 page (also see Messwerte 3) shows your Analog MAF Sensor is working fine. My 3/14/2007 build 328xi shows 13 kg/h @ 660 RPM. It has the Digital MAF Sensor, so the "Raw Values" INPA Screen (F5) shows a raw data reading "168.00" in "mikrosec" for pulse width, with a Value of 10.9 kg/h, presumably at RPM slightly lower than 660 when I printed that screen. Your Analog MAF 325i would have NO entry on either line since you don't have the "Digital HFM Sensor".

Here is the full Bentley explanation, from page 130-15, page 268 of the pdf:
Mass air flow, measurement
3 Series non-turbo engines utilize two different air mass
measurement systems.

Analog mass air flow sensor is used in models produced to
09 I 2006. The sensor, incorporating an electrically heated film in the
air flow stream, sends to the ECM a varying voltage (approx. 0.5-
4.5 volts) representing the mass of the intake air.
The ECM provides operating voltage and ground to the air flow
sensor. As air flows through the sensor, the film is cooled. To
maintain the film at a constant temperature, additional current is
necessary. It is this additional current that is the basis for the input
signal.
If there is no output signal from the air flow sensor, the ECM
operates the engine using throttle position and engine rpm inputs. A
faulty air flow sensor illuminates the MIL.

Digital mass air flow sensor is used in models from 09 I 2006. In
this system, a duty cycle signal corresponds to changes in intake air
mass. This eliminates the need for signal conversion in the ECM.

The intake air temperature sensor is integrated into the mass air flow
sensor. The sensor is an NTC thermistor which receives a 5 volt
reference current and ground from the ECM.

A faulty air flow sensor can produce the following problems:
o Difficult to restart when engine is hot.
o Engine starts then stalls.
o Engine starts and runs only with accelerator pedal depressed.
George
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