Rationality check

P115C, P115D 

Depending on engine speed and throttle position, a theoretically expected maximum and minimum mass airflow is calculated at these engine conditions and compared to the actual measured mass airflow.

If the measured mass airflow from the MAF sensor lies below the theoretically expected minimum mass airflow for a calibrated period of time, a malfunction is detected and a signal fault HFMR is set.

If the measured mass airflow from the MAF sensor exceeds the theoretically expected maximum mass airflow for a calibrated period of time, a malfunction is detected and a plausibility fault HFMR is set.