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 vehicle is a hot film meter (HFM) type. The engine control module (ECM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. The MAF sensor signal is a function of the current required to keep the air flow sensing element at a fixed temperature. 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 in order to maintain the hot film at a constant temperature. The MAF sensor converts the changes in current to a voltage signal that is read by the ECM. The ECM calculates the air flow based on this voltage signal. The MAF sensor uses the following circuits in order to operate:

• The ignition 1 voltage
• The 5-volt reference
• The MAF sensor signal
• The low reference

The 5-volt reference for the MAF sensor is also supplied to additional sensors. For each of the sensors the voltage is supplied on separate ECM terminals. The 5-volt reference is shared by the following sensors:

• The MAF sensor
• The accelerator pedal position (APP) sensor 1
• The fuel tank pressure (FTP) sensor
• The air conditioning (A/C) refrigerant pressure sensor

The low reference circuit of the MAF sensor is shared with the following components:

• The camshaft position (CMP) sensor
• The intake air temperature (IAT) sensor
• The engine coolant temperature (ECT) sensor

If the ECM detects the MAF sensor signal is more than the possible range of a properly operating sensor DTC P0103 sets.