Circuit Description
Intake Air Temperature (IAT) sensor is built into mass airflow 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". Resistor "R" and intake air temperature sensor are connected in series. When resistance value of intake air temperature changes in accordance with changes in intake air temperature, potential at terminal THA also changes. See INTAKE AIR TEMPERATURE SENSOR RESISTANCE table. Based on this signal, ECM increases fuel injection volume to improve driveability during cold engine operation. If DTC P0110 is set, there is an open or short in intake air temperature sensor circuit for .5 seconds. If DTC P0112 is set, there is a short in intake air temperature sensor circuit for .5 seconds. If DTC P0113 is set, there is an open in intake air temperature sensor circuit for .5 seconds. Possible causes are:
- Defective IAT sensor circuit.
- Defective IAT sensor (built into MAF meter).
- Defective ECM.
| Intake Air Temperature °F (°C) | Resistance |
|---|---|
| -4 (-20) | 12.5-16.9 |
| 68 (20) | 2.19-2.67 |
| 140 (60) | 0.50 - 0.68 |