Mass Air Flow Sensor Explained: How It Works and Symptoms of a Bad MAF (ASE Master Mechanic)

In this video, an ASE Master Mechanic explains how the mass air flow (MAF) sensor works, what it does, and the most common symptoms of a bad or dirty MAF sensor. You will learn why a faulty MAF sensor can make your engine run lean or run rich, and what to suspect and check first before replacing any parts. The MAF sensor measures the amount of air entering the engine so the engine computer (ECU/PCM) can calculate the correct amount of fuel. When the MAF sensor fails, gets dirty, or sends inaccurate readings, the air-fuel mixture is thrown off, causing a wide range of drivability problems. Common symptoms of a bad or dirty MAF sensor: Check engine light on Rough idle or unstable idle Engine hesitation or stumbling on acceleration Hard starting or stalling shortly after starting Lack of power, poor throttle response Black smoke from the exhaust (running rich) Poor fuel economy Jerking or surging while driving Engine runs fine when MAF is unplugged (classic test) Common fault codes related to a bad MAF sensor: P0100, P0101, P0102, P0103, P0104 (MAF circuit and performance codes) P0171, P0174 (system too lean) P0172, P0175 (system too rich) Before you replace the MAF sensor, this video also covers what else to suspect: vacuum leaks, intake leaks after the sensor, a dirty air filter, clogged catalytic converter, or wiring issues can all mimic MAF sensor symptoms. In many cases, cleaning the MAF sensor with MAF sensor cleaner can restore proper operation without replacement. This explanation applies to nearly all gasoline vehicles with a MAF sensor, including Honda, Toyota, Ford, Chevrolet, Nissan, BMW, Mercedes-Benz, Volkswagen, Audi, Hyundai, Kia, Subaru, Mazda, Jeep, Dodge, and Chrysler models. For more help, resources, troubleshooting guides, and tools, visit https://www.youcanic.com Search phrases: mass air flow sensor symptoms, bad MAF sensor, MAF sensor cleaning, how MAF sensor works, engine running lean, engine running rich, P0101 code fix, P0171 system too lean, check engine light MAF, MAF sensor test, car hesitates when accelerating, rough idle causes