These units measure the amount of air drawn into the engine which is the most critical determinant utilized by the ECU to optimize the air / fuel mixture. Any malfunction of this device will result in rough idle, poor performance, reduced mileage, and eventually no start.
Mass Air Flow Sensor Types
There are three basic types of air mass sensors:
The first type is the hot wire sensor. It has a small microprocessor, on the main circuit board, which heats a platinum wire contained within the air tube to 100° above the ambient air temperature moving through the air tube. As air moves over the platinum wire voltage must be increased to maintain wire temperature. The ECU reads this voltage and interprets it as the mass air flow.
The second type of air mass sensor is the hot film. With this type, a heated film is used instead of a platinum wire. In this case, the ECU reads the frequency output instead of voltage in order to determine air mass measurements.
The third type of sensor is the Karman vortex. This air mass sensor uses infrared light emitting diodes (LED). A metal air foil oscillates as a result of micro air vortexes within the sensing chamber (tube). These tiny pressure waves cause the light signals between the diodes to produce a frequency that represents the air mass measurement.
The Python Plus Air Mass Sensor
Printed circuit boards are tested for cracks, solder defects, and integrated parts. Failed parts are repaired or replaced.
The hybrid circuit board containing bridge and control circuitry are response tested to various load/temperature ranges. Failed components are replaced.
The precision resistor is tested for electronic integrity.
Platinum wire, film, or diodes are tested and replaced if below standards.
Temperature compensation resistor coating is tested for resistance and integrity. The assembly is replaced if failed.
The final assembly is tested to simulate on-car multi-range performance. "Burn off", duration wire cleansing effect is also tested.