What does an intake air temperature sensor do and works?
An intake air temperature sensor, also known as an IAT sensor, is a device that measures the temperature of the air entering the engine of a vehicle. The intake air temperature sensor (IATS) is one of the sensors that used in the fuel injection and ignition systems of modern vehicles. It is an important component as the temperature of the air can affect the performance of the engine.
The intake air temperature sensor is typically located in the intake manifold channel or in the air filter housing. Some are installed in the air inlet between the throttle body and the air filter, and some are located right behind the air filter.
Also, this IAT sensor is installed together with the Mass Air Flow Sensor, depending on the engine model used by each car manufacturer. The IAT sensor still has the same function, to measure and detect the air temperature that entering the intake manifold.
What is the intake air temperature sensor?
As we mentioned before, the intake air temperature sensor is a device that measures the temperature of the air entering the engine. It is connected to the engine control module (ECM) through a wire.
The ECM uses the information from the IAT sensor to make adjustments to the fuel injection and ignition systems in order to optimize the performance of the engine. For example, if the air temperature is cold, the ECM may adjust the fuel-to-air ratio to compensate for the denser, colder air.
Intake air temperature sensor working principle
The intake air temperature sensor typically uses an electronic component called a thermistor. This thermistor resistance value will change according to changes in air temperature around it.
Mostly, the IAT sensor is used the Negative Temperature Coefficient (NTC) thermistor type, a thermistor in which the value ratio between the air temperature and the resistance value has an inverse ratio.
An inverse ratio for IAT sensor means, the higher the air temperature that enters the intake manifold, the lower the thermistor's resistance value. Vice versa, the lower the temperature of the air that enters the intake manifold, the higher the resistance value in the thermistor.
Look at the graph on the image of the temperature comparison with the resistance value on the thermistor below.
Below is an example of a thermistor working size table related to the resistance value based on its temperature. For vehicle repairs, you must refer to the repair manual specifically for the car.
| Temperature C (F) | Resistance (Kilo ohm) |
|---|---|
| 100 C (212 F) | 2.07 K-Ohm |
| 90 C (194 F) | 2.8 K-Ohm |
| 80 C (176 F) | 3.8 K-Ohm |
| 70 C (158 F) | 5.4 K-Ohm |
| 60 C (140 F) | 7.7 K-Ohm |
| 50 C (122 F) | 11 K-Ohm |
| 40 C (104 F) | 16 K-Ohm |
| 30 C (86 F) | 24 K-Ohm |
| 20 C (68 F) | 37 K-Ohm |
If you pay attention to the table above, when the air temperature value is cold (low), the resistance value will increase (high). Vice versa, when the temperature is hot (high), the resistance value will decrease (low).
One of the main benefits of an IAT sensor is that it allows the ECM to make real-time adjustments to the engine based on the temperature of the intake air. This can help to improve fuel efficiency and reduce emissions, as the engine can operate at its optimal performance levels.
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How does an intake air temperature sensor work?
For how the intake air temperature sensor works, the intake air temperature sensor is given a source voltage of 5 volts from the Engine Control Module (ECM), which will flow into the thermistor through the THA terminal and exit the thermistor via terminal E2 on the ECM. For details, pay attention to the electrical schematic of the Intake Air Temperature Sensor below.
The ECM will supply a voltage of 5 volts into the IAT sensor. When the air entering the intake manifold has a low temperature (cold), the IAT sensor's resistance value will be high (large). As a result, the voltage value that comes out of this IAT sensor will decrease.
When the air temperature entering the intake manifold gets higher (hotter), the resistance value on the IAT sensor will be smaller so that the voltage flowing into the ECM will increase.
The change in the voltage value that occurs on the IAT sensor due to this temperature change will be read by the ECM and used to determine the amount of fuel injected into the engine cylinder.
The longer the opening time of the injector hole, the more fuel is injected. The shorter the opening time of the injector hole, the less fuel is injected.
In conclusion, an intake air temperature sensor is a crucial component in the fuel injection and ignition systems of modern vehicles. It measures the temperature of the air entering the engine and sends this information to the ECM, which makes necessary adjustments to optimize engine performance.