Mass Air Flow (MAF)

A sensor that directly measures the mass of air entering the engine, used as the primary airflow input for fueling.

Mass air flow (MAF) is a sensor mounted in the intake tract that measures the actual mass of air entering the engine, usually via a heated element whose cooling rate tracks airflow. The PCM uses this reading to calculate how much fuel to inject, so MAF accuracy directly drives air-fuel ratio. For a safe tune it matters because a mis-scaled MAF makes the engine run lean or rich without any code, and commanded AFR will not equal delivered AFR until the sensor is calibrated against a wideband. In HP Tuners VCM Editor, MAF calibration lives under Engine > Airflow > Mass Air Flow (the MAF transfer function table in frequency/Hz or g/s). In VCM Scanner you log MAF g/s, MAF frequency, and short/long term fuel trims, then correct the table so logged airflow and trims converge toward zero. Always verify with a wideband before trusting MAF numbers.