MAF Sensor
Mass Air Flow sensor—an electronic sensor that measures the mass of air entering the engine intake system to determine the correct amount of fuel to inject.
The Mass Air Flow (MAF) sensor is a critical electronic engine sensor located in the intake duct between the air filter and the throttle body. Its job is to measure the total mass of air entering the engine's intake system at any given second. This data is transmitted to the engine control module (ECM), which calculates the precise amount of fuel required to maintain the stoichiometric air-fuel ratio (usually 14.7 parts air to 1 part fuel for gasoline).
Most MAF sensors use a "hot wire" or "hot film" design. A tiny wire inside the sensor is electrically heated to a constant temperature. As incoming air flows past the wire, it cools it down. The sensor measures the electrical current needed to keep the wire hot, which is directly proportional to the mass of the air flowing by.
MAF sensors are highly sensitive to dirt, dust, and oil vapor passing through the air filter. If the hot wire becomes contaminated, it will send incorrect readings to the ECM, causing the engine to run too lean or too rich. Symptoms of a dirty or failing MAF sensor include engine hesitation, stalling shortly after starting, a rough idle, poor fuel economy, and a check engine light with codes like P0101.
In many cases, a contaminated MAF sensor can be cleaned using a specialized spray cleaner. If the sensor's internal circuitry is damaged, it must be replaced to restore proper engine performance and drivability.