This generally forces the MAF to underestimate the engine’s intake airflow. In most cases, contamination tends to insulate the metal-film resistor from the air stream, which makes it run hotter than normal. Photo 2: When not serviced correctly, some types of oiled-media aftermarket air filters tend to contaminate hot-wire MAF sensors. In most cases, false air leaks will cause low-speed stalling or rough-idling complaints. “False air” leaking through cracks in the ducting that connects the MAF to the throttle body is a common problem affecting MAF sensor calibration. Although there are different configurations of MAF sensors, most current hot-wire MAFs share the same basic operating principles. In other MAF designs, the IAT is located downstream from the MAF sensor.

Some MAF sensors also include an intake air temperature (IAT) sensor that helps the PCM calculate air density. In some applications, the PCM translates the base data input into a grams-per-second (GPS) data line indicating the metric weight of the air flowing into the engine.

This variation in current flow, which is a base data input, is then translated into a voltage or frequency signal that is sent as a secondary data input to the PCM. The amperage flow through the resistor changes because the electrical resistance of the resistor is responding to the cooling effects of rapidly moving air. In general, a “hot wire” MAF sensor produces an input to the PCM when a low-amperage electrical current is passed through a metal-film resistor suspended in the MAF’s air stream.

E46 mass air flow sensor problems