Circuit Description

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The MAF sensor used on this engine is a hot film meter (HFM) type. The engine control module (ECM) 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 2,500 Hz at idle to near 10,000 Hz at maximum engine load. The MAF sensor frequency signal is a function of the current required to keep the air flow sensing element at a fixed temperature above ambient. The air flowing through the sensor cools the sensing element. The amount of cooling is proportional to the amount of the air flow. As the air flow increases, more current is required to maintain the hot film at a constant temperature. The ECM uses the MAF sensor signal to provide the correct fuel delivery for a wide range of engine speeds and loads. The MAF sensor uses the following circuits to operate:

• A 12-volt reference circuit
• A low reference circuit that is shared with the intake air temperature (IAT) sensor
• A signal circuit

The 12-volt reference circuit of the MAF sensor is also supplied to additional sensors and they are connected within the ECM. The 12-volt reference is shared by the following sensors:

• The MAF sensor
• The crankshaft position (CKP) sensor
• The camshaft position (CMP) sensor bank 1 intake
• The CMP sensor bank 1 exhaust
• The CMP sensor bank 2 intake
• The CMP sensor bank 2 exhaust

The ECM uses the following sensor inputs to calculate a MAF value that is based on an intake manifold model:

• The throttle position (TP) sensors
• The engine speed (RPM)

The ECM compares the actual MAF sensor frequency signal to the calculated MAF model. 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. If the ECM detects the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF model DTC P0101 sets.