Circuit Description

The intake air temperature sensor is built in the mass air flow meter 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 is the greater the thermistor resistance value becomes and the higher the intake air temperature is the lower the thermistor resistance value becomes (See Fig 1).

The intake air temperature sensor is connected to the ECM (See below). The 5 V power source voltage in the ECM is applied to the intake air temperature sensor from terminal THA (THAR) via resistor R.

That is, the resistor R and the intake air temperature sensor are connected in series. When the resistance value of the intake air temperature sensor changes in accordance with changes in the intake air temperature, the potential at terminal THA (THAR) also changes. Based on this signal, the ECM increases the fuel injection volume to improve the driveability during cold engine operation.

Fig 1: Circuit Description - Intake Air Temperature Circuit

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 2: DTC Detecting Condition Table

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

After confirming DTC "P0110, P0112 or P0113", use the hand-held tester or the OBD II scan tool to confirm the intake air temperature in the "DIAGNOSIS/ENHANCED OBD II/DATA LIST/ALL".