Air Flow Meter/Sensor: Description and Operation

Mass Air Flow (MAF) Sensor:

Mass Air Flow (MAF) Sensor Circuit Diagram:

Mass Air Flow (MAF) & Intake Air Temperature (IAT) Sensor Locations:

Purpose:
The Mass Air Flow (MAF) sensor measures the flow of air which passes through it in a given time. The PCM uses this information to monitor the operating condition of the engine for fuel delivery calculations. A large quantity of air movement indicates acceleration, while a small quantity indicates deceleration or idle.

Operation:
The Mass Air Flow (MAF) sensor measures the flow of air which passes through it by monitoring the electrical power required to maintain the temperature of the hot wire sensing element at a specific number of degrees above that of the incoming air. The PCM calculates the temperature of the intake air based on the signal from the intake air temperature sensor, and then heats the air mass sensing element to a specific temperature above that of the intake air by applying an electrical current. As the air enters the sample tube it passes over and cools the sensing element, which then requires additional current to maintain the prescribed temperature difference. The greater the air flow, the greater the cooling effect. The sensor measures the current through the hot wire and generates a frequency signal that varies with the current. The PCM uses this signal to determine the flow rate (in grams per second) of incoming air, for fuel delivery calculations.