Intake Air Temperature (IAT) Sensor, How It Works & Function

What Is IAT Sensor

The intake air temperature sensor or more commonly known as an IAT sensor or air intake sensor is one of the most important parts of the engine’s Electronic Control Unit (ECU).

This is an essential sensor as it maintains a nice emission level and helps the engine to burn the fuel completely and not create any sulfur compounds and lessen the number of nitrogen oxides significantly.

In this powerful article, you are going to learn what the intake air temperature sensor is, its function, and working in easy-to-understand language.

Related Post: Intake Air Temperature (IAT) Sensor Location

What Is Intake Air Temperature (IAT) Sensor

What Is IAT Sensor
What Is IAT Sensor

The Intake Air Temperature (IAT) Sensor, Inlet Air Temperature Sensor, or Air Intake Sensor was labeled with different names before OBD2 (Pre 1995) such as Manifold Charging Temperature (MCT) Sensor, Manifold Air Temperature (MAT) Sensor, or a Charge Temperature Sensor (CTS),

The intake air temperature sensor senses the temperature of the air and sends it to the ECU of the engine. From this signal, the ECU decides the amount of fuel to be injected into the combustion chamber and the rate at which the spark should be provided to the air-fuel mixture.

The IAT sensor helps to measure the relative density of the air with the environment and helps the ECU in calculating the stoichiometric amount of fuel to be injected in the correct ratio.

The intake air temperature is a resistance-based sensor, which exchanges the temperature of the incoming air with the magnitude of resistance, and sends it to the car computer.

The IAT sensor uses a thermistor. A thermistor is an electrical resistor that changes its values according to the temperature around it. Thermistors have two types of coefficients that decide their working mechanism:

  • Positive Temperature Coefficients (PTC) Thermistor
  • Negative Temperature Coefficients (NTC) Thermistor

The Positive Temperature Coefficients (PTC) thermistors increase their resistance with a temperature rise, while the resistance of Negative Temperature Coefficients (NTC) rises with a decrease in temperature.

This change in resistance is detected by ECU in the return voltage from the IAT sensor (through a signal wire), and hence, it determines the air temperature.

Mostly, the IAT sensors are negative temperature coefficient (NTC) thermistors, which means the resistance decreases as the temperature of the sensor increases. A positive temperature coefficient (PTC) thermistor is rarely used these days.

As you know, these days, all cars are based on an electronic fuel injection system, in which the fuel is injected into the combustion chamber through the electronic system.

In an EFI system, you must have the correct air-fuel ratio to increase fuel efficiency. To have a correct air-fuel ratio, you need to know the temperature of the air. It is because colder air is denser than hot air. It uses more fuel due to having more oxygen molecules, which demands more fuel to maintain the correct air-fuel ratio.

So, the temperature of the air is measured by the intake air temperature sensor. The ECU takes the information from the IAT sensor and sends it to the computer for the perfect air-fuel ratio. This is very important as it helps the car’s engine to work properly on a cold day. It also helps your car to maintain fuel economy in hot weather.

Related Post: IAT Sensor Wiring Diagram

Function Of Intake Air Temperature Sensor

Intake Air Tempreture Sensor Inner View
Function Of Intake Air Temperature Sensor

The Intake Air Temperature sensor is the heart of the Electronic Control Unit (ECU) of the car as it determines the efficiency of the combustion in the combustion chamber in the car.

The function of the IAT sensor of the car is to determine the temperature of the air at the intake manifold of the car and transmit the recorded temperature of the air to the ECU of the car.

This is necessary because a change in air temperature changes its density, which affects the number of oxygen molecules per unit area.

Cold air is denser and has more oxygen, which requires more fuel for complete combustion while warm air is lighter and has fewer oxygen molecules in the unit area, which demands a lower amount of fuel.

The computer of the car then uses this related data to calculate the correct stoichiometric amount of fuel to be injected into the combustion chamber for complete combustion of fuel, so the car does not emit any harmful gases into the environment.

Related Post: How To Test Intake Air Temp (IAT) Sensor With Multimeter

How Does Intake Air Temperature Sensor Work

Intake Air Temperature (IAT) Sensor Wiring Diagram
Intake Air Temperature (IAT) Sensor Wiring Diagram

The intake air temperature sensor of the car is a thermistor. A thermistor is an electrical resistor that changes its resistance value with the temperature change.

A 5-volt is applied to this temperature sensor known as the reference voltage by the ECU of the car, and it monitors the voltage that comes back to it by the IAT sensor signal wire.

As a temperature sensor changes its resistance also changes according to the temperature, the temperature sensor allows the voltage back to the ECU according to the temperature. Then ECU analyzes the voltage received back to it by the temperature sensor, the voltage signal received back will tell the ECU about the current temperature of the air.

The ECU is already programmed about the intake air temperature sensor’s input and such amount of voltage received back to the ECU indicates such amount of air temperature. The ECU uses the information obtained from the IAT sensor to maintain the correct air-fuel ratios in the mixture inside the combustion chamber.

Most IAT sensors are Negative coefficient temperature (NTC) thermisters means their resistance decreases with an increase in temperature.

Hot air (high-temperature air) will decrease the resistance and send back high voltage to the ECU while cold air (low-temperature air) will increase the resistance of the sensor and send back low voltage to the ECU. (High temperatures result in high voltage values at the sensor, and low temperatures result in low voltage values).

Due to this, the ECU adjusts the amount of fuel to inject into the combustion chamber to improve the fuel economy. Some intake air temperature sensors are Positive Coefficient temperature thermister means their resistance increases as the temperature increases.

Related Post: 7 Symptoms Of Bad Intake Air Temperature (IAT) Sensor

IAT Sensor Location

The IAT sensor is located in three different locations such as in the air duct of the air charge pipe, in MAP, and in MAF sensors.

Frequently Asked Questions (FAQs)

Is IAT sensor same as MAF sensor?

IAT sensor is short for Intake Air Temperature sensor. It is used to measure the temperature of the air going into the engine. The MAF sensor is short for Mass Air Flow sensor. It is used to measure the amount of air flowing into the engine.

How does IAT affect fuel delivery?

The IAT sensor measures the temperature of the air entering the engine. The ECU uses this information to adjust the amount of fuel injected into the engine. The colder the air, the more fuel is injected into the engine. This is because cold air is denser than warm air and therefore contains more oxygen. More oxygen in the air means that more fuel can be burned, which results in more power being produced by the engine.


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