DTC P0111: Intake Air Temperature Sensor Gradient Too High (FROM 12/2010): Description

WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: View Of Temperature & Resistance Graph

The Intake Air Temperature (IAT) sensor, mounted on the Mass Air Flow (MAF) meter, monitors the IAT. The IAT sensor has a built-in thermistor with a resistance that varies according to the temperature of the intake air. When the IAT drops, the resistance of the thermistor increases. When the temperature rises, the resistance drops. These variations in resistance are transmitted to the ECM as voltage changes.
The IAT sensor is powered by a 5 V supply from the THA terminal of the ECM, via resistor R.
Resistor R and the IAT sensor are connected in series. When the resistance value of the IAT sensor changes, according to changes in the IAT, 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 following conditions are met (2 trip detection logic): In the time period between the warm engine being stopped and the next engine start, change in intake air temperature sensor output below threshold. During engine warm up after a cold engine starts, change in intake air temperature sensor output below threshold.	Mass air flow meter