Circuit Description

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

The following applies to the intake airflow system performance diagnostic that is used in this turbocharged engine:

The manifold absolute pressure (MAP) estimates are used in the engine air flow estimates. Air flow into the intake system must be the same as the air flow out of the intake system, the Intake Air Flow Rationality Diagnostics (IFRD) calculates air flowing out of the engine based on MAP estimates, volumetric efficiency, and RPM.

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

The throttle position (TP)
The barometric pressure (BARO) Bank 1 and Bank 2
The manifold absolute pressure (MAP)
The intake air temperature (IAT) Sensor 1, 2, and 3
The turbocharger boost sensor
The engine RPM

The intake flow rationality diagnostic provides the within-range rationality check for the two mass air flow (MAF), turbocharger boost, manifold absolute pressure (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, turbocharger boost, MAP, and TP obtained from this system of models and calculations are then compared to the actual measured values from the two MAFs, turbocharger boost, MAP, and the throttle position sensors and to each other to determine the appropriate DTC to fail.