What are the symptoms of a bad IAT Sensor? | What is Intake Air Temperature Sensor?

Each engine in a car is a precisely tuned machine with a number of interconnected systems and parts that must operate in harmony to function at their best. The automobile sensors are required for the Engine Control Unit (ECU) to work correctly. For example, the intake air temperature (IAT) sensor detects the temperature of the air entering the engine in order to compute the proper air-fuel composition.

What is an IAT Sensor?

The Intake Air Temperature Sensor keeps track of the temperature of the air entering the engine and transmits that information to the Powertrain Control Module (PCM).

The PCM then guides the appropriate air-fuel mixture ratio for optimal combustion. If the IAT sensor detects heated air entering the engine due to lower air density, the vehicle computer will transmit less fuel to ensure optimal mixes and efficient engine performance.

Therefore, major changes in the engine performance will occur if the IAT sensor fails to work properly.

IAT Sensor

How Does Air Intake Temperature Sensor Work?

This sensor is frequently installed on the top or in between the air filter housing and the intake manifold by auto makers so that it can detect passage of air. When an engine uses a MAF sensor to measure air volume, the MAP sensor also serves as a temperature sensor.

On V-type engines, some manufacturers attach two intake air temperature sensors. This occurs often on engines with separate or divided intake manifolds.

A thermistor is used to measure the temperature of the intake air. Since the temperature may fluctuate, this implies that its signal can also change.

It functions in a manner similar to that of the sensor for coolant. In order to determine the air temperature, the auto computer first supplies a reference or resistance voltage to the sensor, and then reads the voltage it gets back.

The change in air temperature has a direct impact on the return voltage. The voltage that returns to the vehicle computer is impacted by variations in sensor resistance.

Air temperature sensors may also be used in certain automated climate control systems. Some temperature sensors measure both the air outside the vehicle and the air within the passenger compartment.

Please take notice that the temperature sensor for the climate control systems is located outside the engine compartment, thus engine heat won’t have an impact on the readings. Climate control air temperature sensors are often installed in the cowl or behind the grille by automakers.

These temperature sensors for climate control are similar to the IAT sensor. To measure the temperature of the vehicle’s passenger, some employ infrared sensors.


Failure may be caused by a variety of factors:

  • Internal short circuits
  • Damage to the wires
  • Short circuit wiring
  • Mechanical harm
  • Dirty sensor tip

Bad Intake Air Temperature Sensor (IAT) Symptoms

A check engine light on the dashboard is the most prevalent indicator of a faulty intake air temperature sensor. Slow acceleration, a hard cold start, a harsh idle, or misfires are other frequent symptoms.

1) Check Engine Light

The vehicle’s computer keeps track of every system activity. The dashboard’s check engine light will come on if a component or sensor fails. If there are any underlying problems with the system, the engine warning light will let the driver know.

Similarly, the warning light will appear on the instrument panel if the IAT sensor fails. When this light comes on in the instrument cluster, use an OBD2 scanner to figure out what’s wrong with the car.

2) Rough idling

The engine of a vehicle must idle as quietly as possible. A rough idle indicates that one or more components or systems are faulty. It’s possible that a defective IAT sensor is creating the incorrect air-fuel mixture ratio.

If the engine experiences tiny jerks at idling, the intake air temperature sensor is defective. Rough idling may be caused by a variety of problems, much as the check engine light.

3) Bad gas mileage

The air-fuel mixture is regularly adjusted by the engine control unit to attain maximum fuel efficiency. Engine control depends on a number of sensors, including IAT, MAF and MAP sensors to fine-tune the air-fuel mixture adjustment.

Gas mileage will rise or drop dramatically if any of these parts become faulty. If you’re getting less miles per gallon, you may have a bad IAT sensor.

4)  Misfires

Misfires are caused by a lack of combustion in the engine cylinder. This may be caused by a defective spark or an incorrect air-fuel combination.

While accelerating, misfires might be felt as hitches or pauses. You may have an issue with your IAT sensor if you can feel this during acceleration.

5) Drop in Acceleration

The engine control module might mistakenly believe that the air in the engine is colder or warmer than it really is if the intake temperature sensor is malfunctioning. If the PCM receives a false signal, it may miscalculate the air and fuel mixture and slow down the vehicle.

Colder temperatures need more gasoline, which is calculated by the engine control module.

6) Hard Cold Start Condition

Your car’s starting condition is quite important. Your automobile requires a lot and the right quantity of fuel.

An incorrect quantity of gasoline may be injected by your engine management unit if your intake temperature sensor is defective.

7) EGR valve affected

The PCM of certain cars uses air temperature to regulate the EGR valve’s functioning. This indicates that a bad IAT sensor might have an impact on the functioning of the EGR valve. The total engine performance may be affected by a faulty EGR.

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