Every vehicle engine is a fine-tuned machine with several systems and components that work harmoniously for optimum performance. These systems and components malfunction over time and affect the overall engine performance.
While every system and component has a specific function, car sensors are essential for the car computer to function properly.
For instance, the intake air temperature sensor detects the temp of the airflow entering the engine and relates this data to the engine control module (ECM).
Since the intake air temperature sensor can fail and pose drivability issues, motorists should be aware of intake air temperature sensor symptoms and what to do. Here, we’ll discuss intake air temperature sensor functions, symptoms, and how to fix them.
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.
What Does The Air Intake Temperature Sensor Do?
The intake air temperature sensor, also known as the IAT sensor, is a vital component that helps in engine efficiency. It monitors the temperature of the air entering the engine and communicates the data to the powertrain control module (PCM).
The PCM then directs the proper air-fuel mixture ratio for a proper combustion process. For example, if the IAT sensor detects warm air entering the engine since the air density is less, the car computer will send less fuel for proper mixtures and efficient engine performance.
Therefore, if the IAT sensor malfunctions, the engine will suffer significant changes in the engine performance.
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.
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.
Where Is the IAT Sensor Located?
The Intake Air Temperature Sensor is located somewhere on your intake pipes between the air filter and the intake manifold. It is often integrated with the MAF Sensor. Often, it is also installed on the intake manifold.
The intake air temperature sensor’s location is not standard due to different locations in a variety of designs. The best way to locate the IAT sensor in your vehicle is to refer to the service manual provided by your manufacturer.
Intake Air Temperature Sensor Symptoms
A lousy intake air temperature sensor will trigger a check engine light on the dashboard and cause several engine performance issues.
#1. Check engine light.
The car computer monitors all system operations in a vehicle. If any system or sensor malfunctions, it will illuminate the check engine light on the dashboard. The engine warning light will notify the driver of any underlying issues in the system.
In the same manner, if the IAT sensor fails, the warning light will pop up on the instrument cluster. Therefore, whenever this light illuminates on the instrument cluster, diagnose the vehicle with a diagnostic scan tool to know what’s wrong with the system.
#2. Rough idling.
Vehicle engines should idle as smoothly as possible. A rough idling shows one or more systems or components are malfunctioning. It could be you have a faulty IAT sensor causing an improper air-fuel mixture ratio.
If the engine gives small hiccups on idle, the intake air temperature sensor is bad. Like check engine light, several issues can cause rough idling.
#3. Bad gas mileage.
The engine control unit constantly adjusts the air-fuel mixture to ensure maximum fuel economy. Here’s the catch; the engine control unit relies on several sensors like IAT, MAF, and MAP sensors to adjust the air-fuel mixture.
If any of these components go bad, it’ll significantly increase or decrease gas mileage. If you spend fewer miles per gallon, it could mean you have a lousy IAT sensor.
#4. Engine misfire.
Engine misfire is a common BMW intake air temperature symptom. An improper air-fuel mixture in the combustion chamber can cause the engine to misfire.
Again, several factors can cause the engine to misfire. It could be bad spark plugs, lousy spark plug wires, fuel injectors, faulty IAT sensors, etc.
Engine misfire will affect acceleration. Since there are several causes of engine misfires, always diagnose your engine whenever it misfires to track the culprit.
#5. Poor acceleration.
A faulty IAT sensor’s false reading will cause the powertrain control module to think the air is colder or warmer than it is. This will make the PCM miscalculate the air-fuel mixture, leading to a poor or drop in acceleration.
#6. Hard starting in cold weather.
Believe it or not, your car needs more fuel during start-up. It needs more and the correct amount of fuel.
If the car computer injects an obscene amount of fuel during startup because of a lousy IAT sensor, you’ll experience hard starting, especially in cold weather conditions.
#7. EGR valve affected.
In some vehicles, the PCM controls the EGR valve operation with air temperature. This means a lousy IAT sensor can affect the EGR valve operations. A malfunctioning EGR may affect the overall engine performance.
Causes of a Bad Intake Air Temperature Sensor
The air intake temperature (AIT) sensor is a critical component in a vehicle’s engine, and several factors can lead to its malfunction or failure.
Understanding these potential causes can help in diagnosing and fixing issues related to the AIT sensor. Here are some common causes:
#1. Dirt and Debris Accumulation.
Over time, the AIT sensor can get coated with dirt, oil, or other contaminants. This build-up can interfere with its ability to accurately measure the air temperature entering the engine.
#2. Wiring or Connection Issues.
Faulty or damaged wiring, or poor connections, can lead to intermittent or incorrect signals being sent from the AIT sensor to the engine control unit (ECU). Corrosion, frayed wires, or loose connectors are common culprits.
#3. Thermal Stress and Aging.
The AIT sensor is exposed to significant temperature fluctuations, which can cause wear and tear over time. Prolonged exposure to high temperatures can degrade the sensor’s components, leading to failure.
#4. Water or Moisture Damage.
If water, coolant, or other fluids come into contact with the AIT sensor, it can cause short circuits or corrosion. This is often due to leaks or spills in the engine bay.
#5. Faulty Manufacturing or Material Defects.
In some cases, the AIT sensor itself might be of poor quality or have defects from the manufacturing process. This can lead to premature failure or inaccurate readings.
#6. Electrical Interference.
External electrical interference or a malfunctioning ECU can disrupt the signals from the AIT sensor, causing inaccurate temperature readings.
#7. Physical Damage.
The AIT sensor can be damaged by physical impact, such as during engine repairs, accidents, or due to debris hitting the sensor. This can disrupt its functionality.
#8. Improper Installation.
If the AIT sensor is not installed correctly, it might not function as intended. This could be due to incorrect positioning, not securing it properly, or not ensuring a good electrical connection.
Regular maintenance and inspections can help identify and prevent potential issues with the air intake temperature sensor. If a problem is suspected, it’s advisable to have the vehicle checked by a professional to avoid further engine performance issues.
How Do You Test An Intake Air Temperature Sensor?
If you notice any of the symptoms above, test the IAT sensor to know if it is the culprit. In the following sections, we’ll look at how to test an IAT sensor with a multimeter.
Kindly note that an IAT sensor can be an integral part of a MAF or MAP sensor. They can also be independent sensors depending on the vehicle design.
Allow your engine to cool before you start this test.
Testing the IAT sensor resistance
- Disconnect the electrical wiring connector
- Set your multimeter on an auto range or 50k on the OHMs scale
- Turn off the engine and measure the resistance on the IAT sensor. At about 20 degrees centigrade or 68 degrees Fahrenheit, the multimeter should record 37k ohms. At 30 degrees centigrade or 86 degrees Fahrenheit, you should get 24k ohms.
- Reconnect the IAT wiring harness
- Start the engine and allow it to idle for 15-20 minutes. You can also leave it idling until the radiator fan activates to allow the engine to reach normal operating temperature.
- Switch off the vehicle
- Disconnect the IAT wiring connector
- With the intake air temperature sensor unplugged, re-check the sensor resistance across the terminals. At 90 degrees centigrade or 194 degrees Fahrenheit, you should have 2.8k ohms. At 100 degrees centigrade or 212 degrees Fahrenheit, you should have 2k ohms
Consult your service manual for your vehicle-specific temperature and the resistance value of the intake air temperature sensor.
Testing the IAT sensor power and ground
This test aims to ensure the PCM provides the required IAT reference voltage (usually 5 volts) and the ground to process the circuit reading.
- Turn off the vehicle
- Switch the DMM to DC voltage scale
- Disconnect the intake air temperature sensor wiring connector
- Back probe the IAT’s signal wire on the connector using the DMM’s red probe.
- Connect the black probe on the negative battery terminal or the engine ground
- Switch the ignition to the ‘ON’ position. You should have 4.6 to 5 volts
- Return the ignition key to the ‘OFF’ position
- Using the DMM’s black probe, back probe the IAT’s ground wire
- Place the red probe on the positive battery terminal
- Switch the ignition to the ‘ON’ position again. You should have 12 volts approx.
- Return the ignition key
- Reconnect the wiring harness
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:
- Park your car in a safe area
- Prior to doing this test, allow the engine to cool down completely.
- Connect your OBD-II scanner to your vehicle and start the engine.
- 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.
- 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.
- 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.
- Check and measure the sensor wire and the engine control unit if it seems to be right.
How To Fix Intake Air Temperature Sensor Problems?
Fixing a bad air intake temperature (AIT) sensor involves a few potential solutions, ranging from cleaning the sensor to replacing it entirely. Here’s a structured approach to addressing issues with an AIT sensor:
#1. Cleaning the Sensor.
- If the sensor is dirty or covered in debris, carefully clean it using appropriate cleaning solutions (like electronic or sensor cleaner) and a soft brush or cloth. Avoid using harsh chemicals that can damage the sensor.
#2. Repairing or Replacing Wiring and Connectors.
- Inspect the wiring and connectors leading to the AIT sensor. If they are damaged, frayed, or corroded, they should be repaired or replaced to ensure a proper electrical connection.
#3. Sensor Re-calibration.
- In some vehicles, the AIT sensor can be recalibrated. Refer to the vehicle’s service manual for specific instructions on recalibration, as this process can vary depending on the make and model of the vehicle.
#4. Replacing the 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.
#5. Check for Software Updates.
- In some modern vehicles, software updates for the engine control unit (ECU) can resolve issues related to sensor readings. Check if there are any updates available for your vehicle’s ECU.
#6. Reset the Engine Control Unit (ECU).
- After replacing the sensor, it may be necessary to reset the ECU to clear any error codes and allow it to recalibrate to the new sensor. This can often be done by disconnecting the vehicle’s battery for a short period.
#7. Professional Installation.
- If you are not confident in performing the replacement yourself, or if the issue persists after your attempts to fix it, seek professional assistance. A qualified mechanic can ensure the sensor is correctly installed and functioning as intended.
Remember, the exact process for fixing an AIT sensor can vary depending on the make and model of your vehicle.
Always refer to your vehicle’s service manual for specific guidance. Additionally, take appropriate safety precautions when working on your vehicle to avoid injuries or further damage.
IAT Sensor Replacement Cost
The average intake temperature sensor replacement cost is between $40 and $250, depending on the car model and labor costs. An intake temperature sensor costs $20 to $150, and the labor costs $20 to $100.
If your intake temperature sensor is integrated into the MAF sensor, the part cost can increase rapidly. Some MAF sensors cost up to $400.
The replacement of an MAF sensor or intake temperature sensor is often very straightforward and can often be made yourself with basic knowledge.
In some cars, the IAT sensor can be located under the manifold in a difficult location, but this is quite rare.
If you have a new car, you want to look for technical service bulletins for your car models. In some car models, such as Chevrolet or GMC vehicles you will find bulletins about the issue.
FAQs.
Q: Will a bad IAT sensor throw a code?
If the intake air temperature sensor fails and starts sending false readings to the engine control module, it’ll register a P0113 error code. The check engine light will accompany the fault code.
The car computer can log the P0113 fault code because of several parameters. It could be a dirty air filter, damaged wiring, lousy mass airflow sensor, or a faulty PCM.
Q: Does the ambient air temperature sensor affect the engine?
The ambient air temperature does not play any role in the engine efficiency and gas mileage. However, it’ll affect the engine power output. Therefore, do not mistake engine power output for efficiency. Power output and engine efficiency are two different things.
Q: Can you clean an intake air temperature sensor?
The intake air temperature sensor is a vital component that measures intake air temperature. The IAT tip is exposed to air passages and can get dirty. If the sensor becomes dirty, you can clean it for efficient reading.
You may wonder what to use to clean the intake air temperature sensor. If the sensor is dirty, uninstall and clean it with an electronic cleaner.
Final Words
The intake air temperature (IAT) sensor plays a critical role in the overall engine performance.
Since a lousy IAT sensor can affect engine efficiency and optimum performance, if you notice any of the intake air temperature sensor symptoms, fix it as soon as possible.
You can test and fix it following the procedures in this piece or have a professional mechanic fix it.