Air Temperature Sensor ( Ambient / Intake ): Testing and Inspection
Intake Air Temperature SensorElectrical Intake Air Temperature Sensor Diagnosis
General Description
The purpose of this diagnosis is to detect electrical faults. The input signal is analog from a NTC and has to be in a calibrate able range. Short circuit to ground can be detected immediately, short circuit to voltage battery or an open circuit after a delay time. In addition to detect short circuit to voltage battery or an open circuit, the mass air flow must be under a calibratable threshold. If an error symptom is detected, the error counter is debounced.
Substitute value:
A substitute value is calculated if an IAT electrical malfunction is detected. This substitute value is defined as following:
- if no ECT-sensor malfunction is present and ECT is below a calibrate able threshold then IAT is set to a low value
- if ECT-sensor malfunction is present or ECT is above the same calibrate able threshold, then IAT is set to high value
Intake Air Plausibility Check - Plausibility diagnosis
General Description
This diagnosis checks IAT for a Stuck signal. If the vehicle was driven for a mini-mum required distance and time-after-start, then the change in the IAT signal during this period should be above a calibrate able threshold. If this is not the case, a stuck IAT signal is detected.
Flowchart: Intake Air Rationality Diagnosis - Stuck-signal diagnosis
Intake Air Plausibility Check - Gradient diagnosis
General Description
The purpose of this diagnosis is to detect an implausible gradient on the intake-air-temperature sensor signal. The diagnosis checks whether the difference between the measured IAT value and a low-passfiltered (PT1) IAT signal exceeds a calibrate able threshold. If this is the case, a intermittent IAT signal is detected.
Flowchart: Intake Air Rationality Diagnosis - Gradient diagnosis
