Air Flow Meter/Sensor: Description and Operation
ENGINE CONTROL COMPONENTSMass Air Flow (MAF) Sensor
The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire causes it to cool. This hot wire is maintained at 200°C (392°F) above the ambient temperature as measured by a constant cold wire. The current required to maintain the temperature of the hot wire is proportional to the mass air flow. The MAF sensor then outputs a signal to the PCM proportional to the intake air mass. The PCM calculates the required fuel injector pulse width in order to provide the desired air/fuel ratio. This input is also used in determining transmission electronic pressure control (EPC), shift, and torque converter clutch (TCC) scheduling.
The MAF sensor is located between the air cleaner and the throttle body or inside the air cleaner assembly. Most MAF sensors have integrated bypass technology with an integrated IAT sensor. The hot wire electronic sensing element must be replaced as an assembly. Replacing only the element may change the air flow calibration.
Diagram Of Air Flow Through Throttle Body Contacting MAF Sensor Hot And Cold Wire (and IAT Sensor Wire Where Applicable) Terminals:
Typical MAF Sensor:
Typical Drop-in MAF Sensor:
