Circuit Description
Intake air temperature sensor is built into the mass airflow sensor and senses the intake air temperature. A thermistor built in the sensor changes the resistance value according to the intake air temperature. The lower the intake air temperature becomes, the greater the thermistor resistance value, and the higher the intake air temperature becomes, the lower the thermistor resistance value The intake air temperature sensor is connected to the ECM. The 5 volt power source voltage in the ECM is applied to the intake air temperature sensor from terminal THA via resistor. Resistor and the intake air temperature sensor are connected in series. When resistance value of the intake air temperature sensor changes in accordance with changes in the intake air temperature, the potential at terminal THA also changes. Based on this signal, the ECM increases the fuel injection volume to improve driveability during cold engine operation. See Fig 1. DTC P0110 is set when ECM detects an open or short in IAT sensor circuit for .5 second. DTC P0112 is set when ECM detects a short in intake air temperature sensor circuit for .5 second. DTC P0113 is set when ECM detects an open in intake air temperature sensor circuit for .5 second. See Fig 2. Possible causes are:
- Open or short in IAT sensor circuit.
- Faulty IAT sensor.
- Faulty ECM.