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

Intake Manifold Air Temperature Sensor:

Used by the fuel injection ECU:

PURPOSE AND LOCATION
The intake air temperature sensor is located in the intake air tube at the air filter housing. Its signal, with the intake manifold pressure sensor signal is used to calculate the air mass entering the engine.

FUNCTION
The intake air passes through perforations in the sensor and over a bulb which changes electrical resistance depending on air temperature.

The air temperature sensor is of the Negative Temperature Co-efficient (NTC) type.

This means the higher the air temperature, the lower the sensor resistance. The ECU applies a regulated constant voltage to the sensor, and monitors the voltage in the circuit. As temperature increases, sensor resistance decreases, causing a decrease in the measured voltage of the circuit. By monitoring the circuit voltage, the ECU can calculate the intake air temperature, and adjust the air/fuel ratio to meet the specific demands of the engine, at that temperature.