Circuit Description

The intake air temperature sensor is built into 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, the greater the thermistor resistance value, and the higher the intake air temperature, the lower the thermistor resistance value (See Figure).

The intake air temperature sensor is connected to the ECM.

The 5 V power source voltage in the ECM is applied to the intake air temperature sensor from terminal THA via resistor R. That is, 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 also changes. Based on this signal, the ECM increases the fuel injection volume to improve driveability during cold engine operation.

If the ECM detects the DTC P0110, it operates the fail-safe function in which the intake air temperature is assumed to be 20°C (68°F).

Fig 1: Identifying Circuit Description

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Fig 2: DTC Detecting Condition Chart

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

After confirming DTC P0110, use the OBD II scan tool or hand-held tester to confirm the intake air temperature from the CURRENT DATA.