Intake Air Temperature Sensor : Specifications, Working, Circuit, Differences & Its Application

The intake air temperature sensor is essential for optimizing engine performance and supports the electronic fuel injection system’s evolution. Its utilization dates back to the initial EFI systems to determine air density for precise air or fuel ratio calculations. The IAT sensor market is experiencing development worldwide with projections for the coming years. At present, these sensors are standard in most current vehicles and play a significant role within engine management systems. This article elaborates on an intake air temperature sensor, its working and its applications.

What is an Intake Air Temperature Sensor?

An intake air temperature sensor is a two-wire thermistor that measures the air entering temperature into the engine to provide crucial data to the ECU (Engine Control Unit) to optimize fuel delivery & engine performance. This data is very important because the air density changes through temperature.

In addition, the ECU utilizes this data to determine the accurate fuel amount required for optimal combustion. The intake-air temperature sensor function is to supply the ECU with a significant measurement to correct the formation of the mixture & the ignition.

The resistance of the IAT sensor can be changed with temperature, and the ECU understands this resistance change to decide the air temperature. These sensors can be found in various locations, like the intake air tube in between the air filter box & the throttle body or even incorporated into the MAF (mass airflow sensor).

Intake Air Temperature Sensor Working Principle

The intake air temperature sensor’s working principle is to measure the temperature of the air flowing through the engine and transmit this data to the ECU to optimize fuel delivery and engine performance. So, this sensor uses a thermistor whose resistance can be changed with temperature to give a voltage signal that communicates with the air temperature.

When the intake air temperature modifies then the thermistor resistance will be changed accordingly. The ECU gives a reference voltage to this thermistor and the altering resistance results in a changeable voltage signal that is transmitted to the ECU. This voltage signal can be interpreted to decide the intake air temperature and utilizes this data to regulate the air-fuel mixture & other engine parameters for best performance and efficiency.

Specifications:

The specifications of the intake air temperature sensor include the following.

• The IAT sensor is a two-wire thermistor.
• Temperature accuracy normally ranges from ±2°C to ±5°C.
• Response time is fast.
• This sensor resistance can be changed with temperature and normally reduces when the temperature increases.
• Resistance common values at 25°C range from 2.0 kΩ to 5.0 kΩ.
• It is normally mounted in the air filter box or intake manifold.
• This sensor utilizes a standard connector like the Bosch EV1 connector.
• The connector type is AMP SCS (Sealed Connector System).
• Its operating temperature ranges from -40°C to 125°C.
• Its storage temperature is from -40°C to 130°C or above.

Intake Air Temperature Sensor Circuit

The IAT sensor with the ECM circuit is shown below. So the intake air temperature sensor or IAT sensor is given a 5V source voltage from the ECM, and this voltage is supplied into the thermistor throughout the THA terminal & exits the thermistor through the E2 terminal on the ECM.

The ECM supplies a 5V voltage to the IAT sensor. Whenever the air that goes into the intake manifold has a cold temperature then the sensor’s resistance will be large. Thus, the voltage supply value that comes from the IAT sensor will be reduced.

Whenever the air temperature going into the intake manifold gets hotter, then the resistance value above the sensor will be lesser; thus, the voltage supplied into the ECM will rise.

The change within the voltage value that happens on the IAT sensor is because of this temperature change read by the ECM. It is used to decide the amount of injected fuel into the engine cylinder. Here, more fuel can be injected if the opening time is longer.

Similarly, low fuel can be injected if the opening time for the injector hole is shorter. Thus, an intake ATS is a fundamental component within the fuel injection & ignition systems for the current vehicles. So it measures the entering air temperature in the engine to send this data to the ECM, thus making some required adjustments to optimize the engine performance.

IAT Sensor Vs MAF Sensor

The difference between an IAT sensor & a MAF sensor are discussed below.

Advantages

The advantages of the IAT sensor include the following.

• IAT sensors can assist the ECU (Engine Control Unit) to optimize engine performance and fuel delivery by measuring the temperature precisely for the air entering the engine precisely. So it impacts air density directly thus the required fuel amount for combustion.
• The ECU can exactly analyze the proper air-fuel mixture by identifying the intake air temperature which leads to superior fuel economy, decreased emissions, and better engine performance.
• It prevents engine harm by noticing potentially hazardous conditions like detonation occurring by very hot intake air.
• This sensor is significant within motorsport for maintaining reliable performance.
• It plays a significant role in controlling emissions by ensuring the engine functions with the best air-fuel mixture.
• The IAT sensor gives crucial data for engine management, thermal protection and diagnostics by ensuring the engine works in secure parameters.
• Precise air temperature readings let the ECU optimize fuel utilization.
• It is a durable and reliable component.
• These are easy to install into monitoring systems.

Disadvantages

The disadvantages of IAT sensors include the following.

• A faulty IAT sensor can lead to numerous issues like incorrect air ratio or fuel calculations, increased fuel consumption, poor engine performance, etc.
• A faulty sensor can send wrong temperature readings to the ECU (Engine Control Unit) and then miscalculate the perfect air or fuel mixture.
• Poor engines can have different problems like stalling, hesitation, rough idling, decreased engine power, sluggish acceleration, complexity in starting the engine, etc.
• Whenever the air or fuel mixture is wrong, then the engine will become very less efficient which leads to high fuel consumption.
• Ignoring a damaged sensor can lead to durable engine damage because of constantly running with a wrong air or fuel mixture.
• A faulty sensor triggers the MIL to light up with a stored fault code.
• These sensors can face some issues because of rust, dirt, bad connections, damaged wiring, etc.
• The IAT sensor data in some cases is used to handle the EGR (Exhaust Gas Recirculation) valve, thus, a faulty sensor affects operation & emissions EGR.
• A faulty IAT sensor can activate a limp home mode to make sure the IAT circuit is corrected rapidly.

Applications

The applications of intake air temperature sensors include the following.

• The IAT sensor measures the air temperature entering an engine to provide data to the ECU to optimize fuel delivery & engine action.
• The ECU utilizes the IAT sensor’s data to decide the right air-to-fuel ratio with efficient combustion and best engine performance.
• This sensor helps the ECU with another sensor to calculate the air mass of the engine.
• The ECU utilizes the IAT data to regulate the ignition timing for best engine performance in a variety of conditions.
• These are standard components within modern EFI systems that provide critical information for engine control.
• These are used in both diesel and petrol engine applications to optimize the delivery of fuel & engine performance.
• These sensors in motorsport optimize engine act and ensure reliable fuel delivery in varying situations.
• These are used to measure air intake temperature within household or industrial applications.
• Some sensors can also be used in measuring air duct temperature within non-condensing HVAC-based applications.

Thus, this is an overview of the IAT sensor which is a significant component used for engine management. It provides the ECU with information to optimize the mixture of air-fuel & ignition timing. So it ultimately affects performance & fuel efficiency. Here is a question for you: What is a temperature sensor?