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

Intake Air Temperature Sensor:

Air density varies with temperature. Cold air is more dense than hot air, so for a given volume, more fuel is required to mix with cold air. Also hot intake air tends to promote detonation at smaller engine loads and less spark advance. To enable the ECU to compensate for ambient temperature changes, a sensor, mounted on the intercooler air duct to the throttle body, is used to measure the temperature of the air entering the engine.
The intake air temperature sensor is thermistor with a POSITIVE temperature coefficient. Positive temperature coefficient means that the change in resistance is directly proportional to the change in temperature (as temp. increases, resistance increases). The sensor protrudes into the intake air stream at the throttle body. At any given temperature the sensor will have a specific resistance value for that temperature. The ECU measures the resistance in the circuit and from this, calculates the temperature of the intake air.