7 Signs Of A Bad Intake Air Temp Sensor (& Replacement Cost)

What is an Intake Air Temperature Sensor?

The intake air temperature sensor or IAT sensor ha

The intake air temperature sensor or IAT sensor has the core function of monitoring the air temperature entering the engine of your vehicle.

This information is beneficial for the engine control unit or ECU for many functions and calculations, such as calculating the air density for effective ignition timing and fuel efficiency.

The computer system of your engine or the PCM requires this information to stabilize and regulate the combustion engine’s air-fuel ratio. It ensures optimum combustion and efficient fuel consumption.



A faulty air temperature sensor may or may not set a code and turn on the Check Engine light. If the sensor circuit is open or shorted, it will usually set a code. But if it is only reading high or low, or is sluggish due to old age or contamination, it usually will not set a code.

A quick way to check the air temperature sensor is to use a scan tool to compare the air temperature reading to the coolant temperature reading when the engine is COLD. The air temp and coolant sensor readings should closely match (no more than a few degrees difference).

The sensor's resistance can also be checked with an ohmmeter.

Remove the sensor, then connect the two leads on the ohmmeter to the two pins in or on the sensor's wiring connector plug to measure the sensor's resistance. Measure the sensor's resistance when it is cold. Then blow hot air at the tip of the sensor with a blow drier (never use a propane torch!) and measure the resistance again. Look for a change in the resistance reading as the sensor warms up.

No change in the sensor's resistance reading as it heats up would tell you the sensor is bad and needs to be replaced. The sensor reading should gradually decrease if the sensor is a negative thermistor, or gradully increase if it is a positive thermistor. If the reading suddenly goes open (infinite resistance) or shorts out (little or no resistance), you have a bad sensor.

To be really accurate, you should look up the resistance specifications for the air temperature sensor, then measure the sensor's resistance at low, mid-range and high temperatures to see if it matches the specifications. A sensor that reads within the specified range when cold, may go out of range at higher temperature, or vice versa. Such a sensor would not be accurate and should be replaced.

The resistance and/or voltage test specifications for the air temperature sensor on your engine can be found in a service manual, or by subscribing to the service information on the (Vehicle Mfrs Service Information Website or AlldataDIY.

More Information

Manufacturer Part Number SEN039
UPC 657814751316
Weight 0.180000
ICT Manufacturer GM
United States United States
Length Inches 3
Width Inches 1
Height Inches 1

WARNING – This product can expose you to chemicals including lead, which is known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information go to www.P65Warnings.ca.gov

ALUMINUM: Most of the aluminum alloys used today contain some level of lead, usually less than .1%. Lead is known to the state of California to cause cancer and reproductive harm. Most aluminum alloys are physiologically inert in their solid form, and the lead is contained within, however user-generated dust and/or fumes may pose a hazard if inhaled or ingested. Heating beyond a certain temperature may also provide avenues for exposure. STEEL (steel bolts):  Steel is an iron alloy with several metals including Nickel and Chromium. Both Nickel and Chromium are known to the State of California to cause cancer and reproductive harm, respectfully. This warning applies to stainless steels as well.

Q: What are the symptoms of a bad intake air temperature sensor?

A: It’s important to be on the lookout for the symptoms of a failing IAT sensor; the longer the problem goes unaddressed, the more severe the damages become over time. These are the most common symptoms of IAT sensor failure:

Check-engine light is on

Any time you see the check-engine light illuminated, it’s important to have it checked out right away. It could be related to the IAT sensor, but it could also be something more serious.

Rough idling and rough running

Engine stalling, rough idling, engine stumbling, and random surges of power are commonly associated with IAT sensor failure. These are concerning symptoms, and they can only worsen with time.

Difficulty starting the engine

Problems starting your car’s engine are highly inconvenient for everyday life. If you can’t get your car started, have it jumped or tow it to the nearest, most trusted automotive specialist.

Part 2 of 2: Installing the new intake air temperature sensor

Step 1: Install the new sensor. Install the new se

Step 1: Install the new sensor. Install the new sensor by pushing it straight in or screwing it in, depending on the design.

Step 2: Reinstall the electrical connector. To enable the new sensor, you must now reconnect the electrical connector.

Step 3: Reinstall the negative battery cable. As a final step, reinstall the negative battery cable.

As you can see, replacing an intake air temperature sensor is a pretty straightforward process that most can manage with very few materials. Of course, if you’d rather have someone else do the dirty work for you, the team of certified mechanics at YourMechanic offers professional intake air temperature sensor replacement.

Intake Temperature Sensor Diagnostics

The diagnostic procedure of checking if the IAT se

The diagnostic procedure of checking if the IAT sensor has failed is relatively easy. You can do it yourself if you have some basic knowledge and the tools available to you. Have a repair manual for your car ready.

  1. Connect the OBD2 scanner to your car. Turn on the engine.
  2. Check the live data and check the temperature of the IAT sensor. Typically, the temperature readings should be 10 degrees more or less than the vehicle’s ambient temperature, depending on the outside temperature and the engine’s temperature.
  3. If the readings are not realistic, there could be a problem with your IAT sensor or the wirings to it. If the temperature is over 300 degrees or has a low unrealistic value, check the MAF sensor/IAT wires as they can be damaged.
  4. Ohm-measure the Intake temperature sensor and make sure they are the same as your repair manual suggests. If you can find that the ohms are not correct, replace the sensor and remove the trouble codes.
  5. If the sensor seems correct, check and measure the sensor’s wirings and the engine control unit.

How can we help?

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