Circuit Description

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The Mass Airflow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. 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 elements 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:

Ignition 1 voltage.
5-volt reference circuit.
MAF sensor signal.
Low reference circuit.

The 5-volt reference for the MAF sensor is also supplied to additional sensors. For 3 of the sensors, the voltage is supplied on separate ECM terminals. The other sensor is connected at a splice to the same 5-volt reference. The 5-volt reference is shared by the following sensors:

MAF sensor.
Accelerator Pedal Position (APP) sensor 1.
Fuel Tank Pressure (FTP) sensor.
Air Conditioning (A/C) pressure sensor.

The low reference circuit of the MAF/IAT sensor is shared at a splice pack with the following components:

CMP sensor.
Intake Air Temperature (IAT) sensor.
Engine Coolant Temperature (ECT) sensor.

ECM compares the actual MAF sensor voltage signal to the predicted MAF value. The predicted MAF value is based on engine speed, ECT, IAT, and throttle valve opening. 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 that the actual MAF sensor signal is not within a predetermined range of the predicted MAF value, DTC P0101 sets.