Air Temperature Sensor ( Ambient / Intake ): Description and Operation

Intake Air Temperature (IAT) Sensor:

Intake Air Temperature (IAT) Sensor

The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. Low temperature produces a high resistance (100,000 ohms at -38°C/-39°F). A high temperature causes low resistance (70 ohms at 130°C/266°F). The PCM supplies a 5.0 volt signal to the sensor through a resistor in the PCM and measures the voltage. The voltage will be high when the incoming air is cold and low when the air is hot. The PCM calculates the incoming air temperature by measuring the IAT voltage. The IAT sensor signal is used to adjust spark timing according to incoming air density. The scan tool displays temperature of the air entering the engine, which should read close to ambient air temperature when engine is cold. The temperature should rise as underhood temperature increases. If the engine has not been md the Bank 2 HO2S 2 heated oxygen sensors. The front HO2S sensors produces an output signal which indicates the amount of oxygen present in the exhaust gas entering the three-way catalytic converter. The rear HO2S sensors produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the catalysts ability to convert exhaust gases efficiently. If the catalyst is operating efficiently, the front sensors will produce a far more active signal than that produced by the rear sensors.

The catalyst monitor sensors operate the same as the fuel control sensors. Although the Bank 1 HO2S 2 and Bank 2 HO2S 2 sensors main function is catalyst monitoring, they also play a limited role in fuel control. If a sensor output indicates a voltage either above or below the 450 millivolt bias voltage for an extended period of time, the PCM will make a slight adjustment to fuel trim to ensure that fuel delivery is correct for catalyst monitoring.