Both the technicians are correct.
Explanation
Intake air temperature sensor is used in engines of vehicles to monitor the temperature of air entering the engine.
They are basically made of thermistors whose electrical resistance changes according to temperature.
Depending upon the reading and accuracy of intake air temperature sensor, the power-train control module (PCM) will decide about the air and fuel mixture ratio in the engine.
The hot air in engine requires less fuel to operate the engine parts while cold air requires more fuel to operate the engine.
The ratio of air and fuel mixture should be maintained in the engine and it is done by PCM only after getting the input from IAT. So technician B is saying correct.
Also the IAT works as a backup to support the engine coolant temperature sensor by the computer.
As the IAT checks the temperature of outside air, it will help to change the coolant temperature of the engine based on the environment.
Thus technician A is also correct. So both the technicians are correct.
