Circuit/System Description

The mass air flow (MAF) sensor is integrated with the intake air temperature (IAT) sensor. The 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 voltage based sensor. The greater the airflow, the greater the voltage signal. The engine control module (ECM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. The MAF/IAT sensor has the following circuits:

• Ignition 1 voltage circuit
• A shared MAF/IAT low reference circuit
• MAF sensor signal circuit
• IAT sensor signal circuit

The purpose of this diagnostic is to analyze the performance of the MAF sensor by comparing the measured airflow to 2 distinct models when the following operating conditions are met:

• At engine start with Closed Loop inactive.
• Engine running when Closed Loop becomes active.