Located at number 4 cylinder inlet manifold near the block
The ATS sensor measures the air temperature immediately prior to mixture at the fuel injector spray nozzle. It is a negative temperature coefficient thermistor (electrical resistance drops with temperature increase)
By measuring the air temperature the ECU can correct the air fuel ratio to allow for the effect of varying air density. As the density of air is higher at lower temperatures the ECU will adjust the fueling ie. the injector opening time to compensate.