Mass Airflow Sensor
The Mass Airflow (MAF) sensor is located in the air cleaner duct. See Fig 1 . MAF is an air flow meter that measures flow of air entering the engine in grams per second. The Powertrain Control Module (PCM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has an ignition 1 voltage circuit, a ground circuit and a signal circuit. The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2000 Hertz at idle to near 10,000 Hertz at maximum engine load.
The PCM uses the following sensor inputs to calculate a predicted MAF value:
- The Barometric Pressure (BARO) at key ON.
- The Manifold Absolute Pressure (MAP) sensor.
- The Intake Air Temperature (IAT) sensor.
- The Engine Coolant Temperature (ECT) sensor.
- The Throttle Position (TP) sensor.
- The engine speed (RPM).
The PCM compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison will determine if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition.