DTC P0112: Intake Air Temperature Circuit Low Input; DTC P0113: Intake Air Temperature Circuit High Input: Description

• The intake air temperature sensor, mounted in the mass air flow meter sub-assembly, 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 hybrid vehicle control ECU as voltage changes (see Fig. 1 in Fig 1).
• The intake air temperature sensor is powered by a 5 V supply from the THA terminal of the hybrid vehicle control ECU, via resistor R which is located inside the hybrid vehicle control ECU.
• 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 hybrid vehicle control ECU increases the fuel injection volume when the engine is cold to improve driveability.

  HINT: 

  When either DTC P0112 or P0113 is set, the hybrid vehicle control ECU enters fail-safe mode. During fail-safe mode, the intake air temperature is estimated to be 20°C (68°F) by the hybrid vehicle control ECU. Fail-safe mode continues until a pass condition is detected.

Fig 1: Resistance And Temperature Graph

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HINT: 

When any of these DTCs are set, check the intake air temperature by entering the following menus: Powertrain / Engine and ECT / Intake Air.