Intake Air Temperature Sensor

Intake Air Temperature Sensor

The IAT sensor is a thermistor device mounted inside the MAF sensor. It provides an input signal to the ECM proportional to the temperature of air passing through the inlet duct into the engine. A DTC is recorded if the voltage input signal from the sensor to the ECM is outside pre-defined thresholds at the high or low end of the scale.

High/Low Input Failure
These are continuous monitors. The voltage from the sensor is compared to a failure threshold defined in the software. If the voltage is below the low threshold, then a timer starts to increment. Once this timer exceeds another threshold, then a failure flag is set and a DTC is stored. If the voltage is over the high threshold defined in the software, then a timer starts to increment. Once this timer exceeds a threshold, then a failure flag is set and a DTC is stored.

Range/Performance Check 1
If engine speed and intake airflow is sufficient, the ECT is low enough and the air temperature sensor voltage is lower than calibrated constants, then a monitoring failure judgment is made.

If after a calibrated period has elapsed the voltage from the sensor is greater than a calibration constant then a monitoring normal judgment is made.

Range/Performance Check 2
At intervals of approximately 2 seconds, the IAT is sampled to monitor for rapid drop in air temperature. If the change in IAT (over a 6 second period) is greater than a calibration constant then a monitoring failure judgment will be made. A normal judgment is made if the change in IAT change is less than this calibrated value.