Bad Intake Air Temperature Sensor: Symptoms, Causes, & How to Fix It

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 data of the sensors is required for the powertrain control module (PCM) to work efficiently. 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. When the IAT sensor goes bad, it produces different symptoms. This article explains the bad intake air temperature sensor symptoms, its causes, and how to replace it.

What is an IAT Sensor?

The Intake Air Temperature Sensor, or IAT 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 understands the sensor data and delivers 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 engine performance will occur if the IAT sensor fails to work properly.

How Does Air Intake Temperature Sensor Work?

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

IAT Sensor

On V-type engines, some manufacturers attach two intake air temperature sensors. This often occurs 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.

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.

When the IAT sensor goes bad, it produces one or more of the below-given symptoms:

  • Check Engine Light
  • Rough idling
  • Poor gas mileage
  • Hard starting condition
  • Poor acceleration
  • Emissions test failure
  • EGR valve affected
  • Black smoke from the exhaust
  • Misfires

1) Check Engine Light

Check engine light flashing

The vehicle’s powertrain control module (PCM) 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, when the PCM monitors an issue with the IAT sensor, it triggers the check engine light. When this light comes on your vehicle dashboard, use an OBD-II scanner to figure out what’s wrong with the car.

Read More: Causes of Check Engine Light Flashing

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.

Rough Idling

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, such as the check engine light.

3) Poor Gas Mileage

Poor fuel economy

Poor gas mileage is one of the clear signs of a faulty intake air temperature sensor. The air-fuel mixture is regularly adjusted by the PCM to attain maximum fuel efficiency. The PCM 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 fewer miles per gallon, you may have a bad IAT sensor.

Read More: Bad MAP Sensor Symptoms and Causes

4) Hard Starting Condition

Hard Starting condition due to a faulty IAT Sensor

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. This may make your car hard to start.

5) Poor Acceleration

acceleration problems due to a faulty intake air temperature sensor

The PCM 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) Emissions Test Failure

Failed Emissions Test

A faulty IAT sensor may cause your car to fail an emissions test because it may cause higher emissions of harmful pollutants due to improper air-fuel mixtures.

7) EGR Valve Affected

EGR Valve

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.

Read More: Bad EGR Symptoms and Causes

8) Black Smoke from the Exhaust

Black Smoke from the Exhaust Pipe

An excessively rich air-fuel mixture due to a faulty IAT sensor can result in black smoke coming from the exhaust pipe, indicating unburned fuel.

9) Misfires

Engine Misfires, signs of bad intake air temperature sensor

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.

Causes of a Bad IAT Sensor

An IAT sensor goes bad because of one or more of the below-given causes:

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

Where Is the IAT Sensor Located?

The Intake Air Temperature Sensor is positioned somewhere between the air filter and the intake manifold on your intake pipes. It is often used in conjunction with the MAF Sensor. It is often mounted on the intake manifold.

IAT Sensor location

Due to a diversity of designs, the position of the intake air temperature sensor is not conventional. When looking for an IAT sensor in your car, you should consult the service manuals given by your manufacturer.

How to diagnose an IAT Sensor

Test the IAT sensor to see whether it’s the cause of any of the symptoms listed above. Using an OBD2 scanner, we’ll examine how to troubleshoot an IAT sensor. Please be aware that a MAF or MAP sensor may have an IAT sensor as well. Depending on the vehicle’s design, they may also be separate sensors.

Follow the below-given steps to diagnose an intake air temperature sensor:

  1. Park your car in a safe area
  2. Prior to doing this test, allow the engine to cool down completely.
  3. Connect your OBD-II scanner to your vehicle and start the engine.
  4. Check the real-time data and the IAT sensor’s temperature. The temperature readings should typically be 10 degrees higher or lower than the car’s ambient temperature, depending on the temperature both inside and outside the vehicle as well as the temperature within the engine.
  5. If the results do not seem to be realistic, there might be an issue with your IAT sensor or the connection to it. Check the MAF sensor/IAT wiring for damage if the temperature exceeds 300 degrees or has an implausible low reading.
  6. Check to see whether the intake temperature sensor’s ohm readings match those recommended by your service manual. The fault codes may be cleared if the sensor’s ohms are found to be incorrect.
  7. Check and measure the sensor wire and the engine control unit if it seems to be right.

How to Replace an Intake Air Temperature Sensor

Clean or replace the IAT sensor after testing if it is found to be defective. Follow the below-given steps to replace and IAT sensor:

  • Turn off the engine and let it cool down
  • Disconnect the negative connection of the battery.
  • Unplug the IAT sensor wire harness.
  • Locate the intake air temperature (IAT) sensor.
  • If the IAT sensor is installed on the intake manifold, unscrew it and gently remove it from the intake duct.
  • Properly inspect the old sensor. If it is dirty, properly clean it. If the sensor is damaged, you need to replace it.
  • Install the new IAT sensor and reconnect the wiring harness.
  • Reconnect the negative terminal of the battery.
  • Reconnect all other back back on their places.
  • Perform a test drive to check the functionality of the IAT sensor. 

IAT Sensor Replacement Cost

The replacement of the intake air temperature sensor depends on the make and model of the vehicle and labor charges. The average replacement cost of the IAT sensor is from $30 to $260. In this cost, the labor cost is between $10 to $100, while the part itselt cost is from $20 to $160.

Adding an intake temperature sensor to your MAF sensor will quickly raise the component price. MAF sensors may cost up to $400.

FAQ Section

What is the Function of the IAT Sensor?

The main function of the inlet temperature sensor (IAT sensor) is to measure the air temperature entering the engine’s intake manifold and send this data to the vehicle’s powertrain control module (PCM). The PCM uses this data to adjust the air-fuel ratio and ignition timing.

Can you clean an intake air temperature sensor?

The sensor that detects the temperature of the intake air is critical. IAT tips are exposed to air passageways and might accumulate dirt. You may clean the sensor if it becomes dirty to get better readings.

Can a bad intake air temperature sensor cause misfire?

Misfires may be caused by a faulty intake air temperature sensor. The intake air temperature sensor data is used by the engine’s computer to calculate the amount of fuel to be injected into the engine. The engine may misfire if the sensor doesn’t provide reliable data.

Will a bad IAT sensor throw a code?

A P0113 error code will be shown if the intake air temperature sensor malfunctions and begins giving the engine control module incorrect values. In addition to the problem code, the check engine light will flash. Several other factors allow the PCM to record the P0113 trouble code. A clogged air filter, frayed wiring, a subpar mass airflow sensor, or a problematic PCM are all potential causes.

Does the ambient air temperature sensor affect the engine?

There is no correlation between ambient air temperature and engine efficiency or gas mileage. However, this will have an impact on the engine’s output. Therefore, you should not confuse the power output of the engine with its efficiency. Engine efficiency and power output are two separate concepts.

What are the signs of a bad IAT Sensor?

  • Check Engine Light
  • Rough idling
  • Poor gas mileage
  • Hard starting condition
  • Poor acceleration
  • Emissions test failure
  • EGR valve affected
  • Black smoke from the exhaust
  • Misfires

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