How a mass air flow sensor works (my view) The MAF (mass air flow) sensor is mounted in a vehicle’s engine air intake tract and its job is to measure the volume and density of air being drawn into the engine. The MAF (mass air flow) sensor is basically a little heater which heats up to a predetermined temperature that is monitored by the PCM when the PCM detects that the actual MAF sensor temperature is not within the predetermined expected range of the calculated MAF value it sets a Malfunction indicator lamp (MIL) illumination (a.k.a. check engine light) How a mass air flow sensor really works A mass air flow sensor has a small electrically heated wire (hot wire) and a small temperature sensor installed close to the hot wire. The temperature sensor measures the temperature of the air near the hot wire. When the engine is idling, a very little air flows pass the hot wire, so it takes very small electrical current to keep the wire hot. When you press the gas, the throttle opens allowing more air to flow over the hot wire. The passing air cools the hot wire down; the more air flows over the wire, the more electrical current is needed to keep it hot. The amount of this electrical current is proportional to the amount of the air flow. A small electronic chip installed inside the air flow sensor translates the amount of this electrical current into a digital signal that is sent to the engine computer (PCM). The PCM uses the air flow signal to calculate the proper amount of fuel injected into the cylinders in order to keep the air/fuel ratio at the optimal level. This is needed to keep the exhaust emissions low without sacrificing the engine performance. In addition, the PCM uses the air flow readings to determine the shift points of the automatic transmission; so if the air flow sensor doesn’t work properly, the automatic transmission might shift gears differently. Note: Some MAF sensors also incorporate an air intake temperature sensor, which is another value used by the PCM for optimal engine operation. Closely related MAF circuit trouble codes include: ⦁ P0100 Mass or Volume Air Flow “A” Circuit Malfunction ⦁ P0101 MAF Circuit Range/Performance ⦁ P0102 Mass or Volume Air Flow “A” Circuit Low Input ⦁ P0103 Mass or Volume Air Flow “A” Circuit High Input ⦁ P0104 Mass or Volume Air Flow “A” Circuit Intermittent Note: other codes may be present if you have P0100 codes. You may have misfire codes or O2 sensor codes, so it’s important to take a “big picture” look at how the systems work together and effect each other when doing a diagnosis. P0100 codes Symptoms may include ⦁ Malfunction indicator lamp (MIL) illumination (a.k.a. check engine light) ⦁ Rough running engine ⦁ Black smoke from tail pipe ⦁ Stalling Engine hard start or stalling after it starts ⦁ Possible other driveability symptoms Possible Causes ⦁ Dirty or contaminated mass air flow sensor ⦁ Failed MAF sensor Intake air leaks ⦁ MAF sensor electrical harness or wiring problem (open, shorted, frayed, poor connection, etc.) ⦁ Clogged catalytic converter on some models (GMC/Chevrolet mainly)]]>
Mass Air Flow Sensor (MAF) – What"s it do and How it works