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