4.18.1 Sensor Stuck in Range

This monitor checks that the inlet air temperature sensor is not stuck at a value within its normal operating range. It runs continuously provided the engine speed is above a threshold and will fail if the sensor signal has not changed by more than a pre-determined amount after the vehicle has been driven above a certain speed for at least a pre-determined time and also operated at idle for a calibrated time.

The inlet air temperature sensor reading is compared with a maximum and a minimum value. If it is above the maximum, then this is updated to the current sensor reading. If the sensor reading is below the minimum, then this is updated to the current sensor value. A test value is calculated by subtracting the minimum from the maximum value.

When the entry conditions for the driving check are true, then a timer is incremented, if these conditions cease to be true, then the timer is reset to zero. When the timer exceeds a threshold, then a flag is set to indicate that sufficient driving has been completed. The entry conditions for the driving check require that the mass air flow is within a window and the vehicle speed is above a threshold.

When the entry conditions for the idle check are true, then a timer is incremented, if these conditions cease to be true, then the timer is reset to zero. When the timer exceeds a threshold, then a flag is set to indicate that sufficient idling has been completed. The entry conditions for the idle check require that the mass air flow is below a threshold, the engine coolant temperature is above a threshold, the engine oil temperature is above a threshold, the driving check has been completed and the vehicle speed is below a threshold.

Once both operating condition flags have been set, then the test value is compared to the fault threshold, if this is exceeded, then a normal judgment is made. If the threshold has not been exceeded and the engine coolant temperature is above a calibrated value, then a fault will be set.

This diagnostic is identical for both left and right-hand sensors for the super-charged engine. The left-hand sensor uses P00AB and the right-hand sensor P0111.