How To Test IAT Sensor With Multimeter

Do you own a vehicle with an IAT sensor but don’t know how to test it? We’re here to help! This post will review the fundamentals of using a multimeter to test IAT sensors. Knowing how to use a multimeter and understanding the results of these tests can save you time and money when diagnosing problems with your vehicle in the future. Understanding an IAT sensor is critical for maintaining peak performance in your car, so let’s learn more about what these sensors do!


What are an IAT sensor and its function?

IAT (Intake Air Temperature) sensor measures the temperature of the air entering an internal combustion engine. Its primary function is to inform the engine control unit about the amount and density of air entering an engine so that it can adjust fuel delivery accordingly. This information helps optimize fuel economy, reduce emissions, and maintain performance levels. In some cases, IAT sensors are also used to detect a sudden increase in air intake temperature, which could indicate imminent engine damage due to detonation or knock.

IAT sensors are typically installed near or after the throttle body, where they can measure incoming air temperatures before other components like turbochargers or intercoolers heat them. Accurate measurements help prevent problems such as pre-ignition, detonation, and engine knock. IAT sensors are typically connected to the engine control unit, which then uses this information to adjust fuel delivery and timing. This helps provide optimal performance, fuel economy, and emissions levels for a given driving condition.

Overall, IAT sensors play an essential role in modern internal combustion engines by helping detect changes in air intake temperatures that could affect engine performance or cause damage. Accurate readings from IAT sensors also allow the engine control unit to adjust parameters like fuel delivery and timing for better efficiency, lower emissions, and enhanced performance overall.

Symptoms Of Bad IAT Sensor

Check Engine Light:

The most common symptom of a bad IAT Sensor is the illumination of the check engine light on your vehicle’s dashboard. This signal indicates that the ECU has detected an abnormal reading from the IAT sensor and identified this as a potential problem.

Poor Fuel Economy:

Increased fuel consumption can signal that your IAT sensor is not functioning correctly, resulting in more fuel being used than necessary for combustion processes within your engine.

Hard Starting/Tough Idling:

If you experience difficulty starting your car or it is idle roughly, these could be signs that your IAT Sensor needs attention due to malfunctioning or contamination.

Unusual Engine Noise:

An abnormal engine noise, such as knocking or ticking, can be a symptom of a bad IAT sensor not correctly regulating the air-fuel ratio.

Poor Acceleration:

If your car has reduced acceleration or power capabilities due to a malfunctioning IAT Sensor, it is vital to resolve the issue immediately.

Hesitation/Stumble on Acceleration:

You may experience hesitation when accelerating due to a faulty IAT sensor signaling an incorrect air-to-fuel ratio. It can cause the engine to take longer than usual to respond and puts added stress on other components within your vehicle’s engine.

Rich Fuel Mixture:

This is characterized by a distinctive smell of gasoline in the exhaust fumes and can lead to poor fuel economy.


If you experience misfiring when accelerating, this could be a sign that your IAT Sensor is not correctly regulating the air-fuel ratio and needs to be replaced as soon as possible.


Your vehicle may backfire due to an accumulation of unburned fuel caused by an incorrectly functioning IAT sensor.

Leaking Fluids:

Bad IAT sensors can cause engine fluids such as oil or coolant fluid to leak, resulting in further damage and problems for your vehicle if left unchecked. You must take care of any leaks immediately if they are noticed.

You must recognize these symptoms and take appropriate action to ensure the health of your vehicle’s engine. Contact a qualified mechanic if you suspect your IAT Sensor may malfunction. They will be able to diagnose the issue and advise you on what repairs need to be done to get your car running properly again.

How To Test IAT Sensor With Multimeter

Testing the Intake Air Temperature Sensor with a digital multimeter is essential to ensuring your vehicle’s optimal performance and safety.

1. Preparing to Test:

  • Disconnect the Intake Air Temperature sensor from the electrical connector.
  • Set the Digital Multimeter to a reading of 50K on the Ohms scale.

2. Measuring Signal Resistance at Different Temperatures:

With the car engine off, measure signal resistance across terminals of the IAT Sensor and record your readings. At 20 °C, the reading should be 37K ohms; at 30 °C, it should be 24K ohms.

3. Testing Results with Engine Running :

  • Connect the Intake Air Temperature sensor back to its electrical connector before starting up your engine for around 20 minutes at idle speed.
  • As the temperature rises, turn off your engine.
  • Disconnect the IAT Sensor again and measure signal resistance across its terminals. Compare this to your initial readings when the engine was off.

4. Reviewing Results:

  • If the readings are within the acceptable range mentioned above (37K ohms at 20 °C and 24K ohms at 30 °C), then your IAT sensor is functioning correctly.
  • If not, it may be time to replace or recalibrate the IAT Sensor to ensure your vehicle’s safety and proper performance.

To ensure optimal performance, you should repeat this test regularly or whenever there is a noticeable change in engine performance. By following the above steps, you can ensure your car runs smoothly and safely.

Frequently Asked Questions:

What is the IAT sensor’s voltage range?

The IAT sensor requires a 5V DC voltage supply for proper operation. The temperature range for the IAT sensor is -40°C to 135°C. Therefore, it is necessary to use a multimeter with a wide voltage range that can accurately measure lower and higher voltages. It is vital to ensure that the multimeter has enough sensitivity to detect small changes in the IAT sensor’s current values.

What is the perfect ohm value for an IAT sensor?

The resistance should be around 2400 ohms at 86°F (30°C). To test your IAT sensor with a multimeter, set the multimeter to the Ohm setting. Then, connect the multimeter’s two leads across the IAT sensor terminals and measure the resistance. If it is out of specification, your IAT sensor may need to be replaced.

What should I do if my IAT sensor fails the test?

If your IAT sensor fails the test, the most likely cause is an electrical malfunction or incorrect connection. First, try replacing any faulty wiring or components before attempting to diagnose further. If this does not solve the issue, consult a professional for further assistance or replacement of the IAT sensor itself. With proper testing procedures and standard maintenance practices, you can extend the life of your IAT sensor and keep it functioning optimally.


Finally, testing an IAT sensor with a multimeter requires basic device knowledge and familiarity. Identifying and connecting each wire is critical, considering any polarity correctly. Once connected, you can use the multimeter to test the sensor’s functionality and ensure that it provides accurate readings. With this information, you should be able to troubleshoot your IAT sensor effectively if it stops working correctly.

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