Air Flow Meter/Sensor: Description and Operation

The Bosch MAF Sensor is of the hot wire type. Current is supplied to the sensing wire (hot wire) to maintain a calibrated temperature, and as air flow increases or decreases the current will vary. This varying of current causes a voltage drop within the meter circuitry which is directly proportional to the incoming air mass. The ECM supplies a current limiting 5 volt source on the signal line. The MAF sensor draws approximately .4 volts with a low air flow and up to 5 volts with a high air flow (during wide open throttle applications).