Intake Air Temperature Sensor (IATS) is NTC thermister which voltage gets low if the temperature comes to be high. Installed inside of both MAFS and BPS, it senses intake air temperature. In case of EURO-4 diesel engine, IATS is installed in front of turbocharger (inside of MAFS) and behind it (inside of BPS). Comparing air temperature from both sensors (one is intake air temperature, the other is air temperature passing through turbo charger), more accurate sensing of intake air temperature is possible. With intake air temperature signal, ECM performs EGR control correction and fuel injection quantity correction. (MAFS is needed for EGR FEED BACK control in electronically controlled diesel engine. The calculation of air density at certain temperature is required to perform EGR FEED BACK control correctly.)

P0098 is set when the voltage above 4965mV - maximum output voltage of IATS (integrated with BPS) - is detected for more than 2.0 sec.. This code is due to 1) open or 2)short to battery in IATS signal circuit.