Circuit Description

The engine control module (ECM) uses the following information to calculate an expected airflow rate:

• The throttle position (TP)
• The barometric pressure (BARO)
• The manifold absolute pressure (MAP)
• The intake air temperature (IAT)
• The engine RPM

The intake airflow system performance diagnostic provides the within-range rationality check for the mass air flow (MAF), MAP, and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing separate models for the intake system.

The estimates of MAF, MAP, and TP that are obtained from this system of models and calculations are then compared to the actual measured values from the MAF, MAP, and TP sensors and to each other to determine the appropriate DTC to fail.