– Intake air leaks
– Dirty mass air flow sensor
– Dirty mass air filter
– Mass air flow sensor harness is open or shorted
– Mass air flow sensor circuit poor electrical connection
– Engine stall
– Engine running rough
– Excessive fuel consumption
– Excessive smoke
The Mass Air Flow (MAF) sensor measures the amount of air ingested by the engine. The direct measurement of the air entering the engine is more accurate than calculating the airflow from the Manifold Absulte Pressure (MAP), the Intake Air Temperature (IAT), and the engine speed (speed/density). The MAF sensor has a battery feed, a ground, and a signal circuit.
The MAF sensor used on this engine is a hot wire type. This engine uses the MAF sensor in order to measure air flow rate. The MAF output frequency is a function of the power required to keep the air flow sensing elements (hot wires) at a fixed temperature above the ambient temperature. Air flowing through the sensor cools the sensing elements. The amount of cooling is proportional to the amount of air flow. The MAF sensor requires a greater amount of current in order to maintain the hot wires at a constant temperature as the air flow increases. The MAF sensor converts the changes in current draw to a frequency signal read by the Powertrain Control Module (PCM). The PCM calculates the air flow (grams per second) based on this signal.
The PCM monitors the MAF sensor frequency. The PCM determines if the sensor is stuck low, stuck high, not providing the airflow value expected for a given operating condition, or that the signal appears to be stuck based on a lack of signal variation expected during the normal operation. This diagnostic tests for too low an airflow rate.