Genuine 2011 BMW 335i Mass Air Flow Sensor

2011 BMW 335i Mass Air Flow Sensor Parts Questions & Experts Answers

• Q: What are the differences between the analog and digital mass air flow sensors, and what issues can a faulty air flow sensor cause on 2011 BMW 335i?

  A: Non-turbo engines of 3 Series use two kinds of air mass measurement techniques. The mechanical mass air flow sensor which is utilised in models up to Sept 2006 employs an electrically heated film in the air flow stream which provides a variable voltage 0.5V to 4.5V to the ECM proportional to the mass of intake air. From the ECM, operating voltage/ground is applied to the air flow sensor and as the film passes through it, the air cools it and hence draws more current to maintain a steady temperature - the input signal. Without the output signal from air flow sensor, then the ECM has to work with throttle position and engine rpm signals to run the engine and the faulty sensor sets on MIL. Since September 2006 a digital mass air flow sensor is used where a duty cycle signal relates to the change of intake air mass and a signal does not require further conversion in the ECM. The intake air temperature sensor is incorporated within the mass air flow sensor and is a type NTC thermistor which receives 5-volt reference current and ground from the ECM. If the air flow sensor is bad it can make the car hard to start when the engine is hot; start then die; run only when the accelerator pedal is pressed.