4.14.2 Range/Performance Failure

This monitor runs continuously so long as the entry conditions are met. The Mass Airflow Sensor monitor compares the measured airflow with an estimated airflow, which is calculated by a model. The model that calculates the estimated airflow uses a look-up table using engine speed and throttle angle as inputs. These are used to derive base and compensation values for intake air temperature, atmospheric pressure, EGR rate and VVT, from which the estimated airflow is calculated.

Judgement as to whether the Mass Airflow sensor is behaving correctly is made after the entry conditions have been fulfilled and the differences between the measured and estimated values are below calibrated thresholds. The Mass Airflow sensor is faulty if when the entry conditions are met, the difference between the actual and estimated values is greater than a calibrated threshold. The monitor has the ability to make a normal judgement followed by a failed judgement or vice versa as the monitor runs continuously whilst the entry conditions are met.