DTC P0111: Intake Air Temperature Sensor 1 Circuit Range / Performance [08/2013 - ]: Description

WARNING: This page is about a different car, the 2015 Lexus IS 250C and 2014 Lexus IS 250C. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Resistance VS Temperature Graph

The intake air temperature sensor, in the mass air flow meter, monitors the intake air temperature. The intake air temperature sensor has a built-in thermistor with a resistance that varies according to the temperature of the intake air. When the intake air temperature becomes low, the resistance of the thermistor increases. When the temperature becomes high, the resistance drops. These variations in resistance are transmitted to the ECM as voltage changes (see Fig. 1).
The intake air temperature sensor is powered by a 5 V supply from the THA terminal of the ECM, via resistor R which is located inside the ECM.
Resistor R and the intake air temperature sensor are connected in series. When the resistance value of the intake air temperature sensor changes, according to changes in the intake air temperature, the voltage at terminal THA also varies. Based on this signal, the ECM increases the fuel injection volume when the engine is cold to improve driveability.

DTC No.	DTC Detection Condition	Trouble Area
P0111	When either of the following conditions is met (2 trip detection logic): The intake air temperature change from the previous warm-up to the following trip is small The change in the intake air temperature after engine start is less than the threshold value	Mass air flow meter