Rationality Check

The signal is checked for rationality against the Intake Air Temperature sensor. When the entry conditions have been met the difference between the two sensors is calculated. If the difference is greater than 30 °C for a predefined period of time then a failure is registered. If the problem occurs on two drive cycles then the MIL will illuminate. The DTC which is logged depends on whether the ambient air temperature sensor signal is lower or higher than the intake air temperature sensor.