IAT Sensor

IAT sensor (Intake Air Temperature) basically monitors the temperature of the air coming into the engine. The PCM uses this temp information to adjust the air/fuel based on the air temperature/density.

IAT Sensor test on the Jeep YJ

Where are TPS Sensors located?

On Jeeps the sensor is located in the intake manifold toward the back behind the throttle body. This includes both the 4.0 I-6 and the 2.5 I-4. Most cars have the sensor in the air box where the filter is located or upstream in the tubing going to the throttle body.

Will it trigger the check engine light if the sensor is faulty?

Yes it can light the check engine light. Often times it can also make the engine run too rich or possibly lean. If the engine is running on the lean side, you may here slight pinging coming from the engine. Also when it’s cold outside the engine may idle poorly if the IAT sensor is faulty.

Why does it fail?

They normally fail due to the heat under the hood. Some vehicles it's inside the air box where the air filter is located or upstream in the air tube going to the throttle body. Debris can collect on the sensor and cause it to prematurely go bad. Also if the vehicle has a lot of blow by from worn piston rings allowing oil to get into the air intake system, the oil will collect in the sensor causing it to go bad.

How do you test it to see if they are bad?

To test you need a multi-meter and a hot hair dryer.

Make sure that the engine is cool to ensure accurate testing. Unplug the sensor from the engine harness. Remove it from the engine. Test the sensor leads with your ohm meter while the sensor is still cool, note the current temperature. This is your base reading, so write this number down to refer to it later. Turn on the hair dryer; put the sensor in the pathway of the hot air to simulate hot air coming into the engine. Measure the leads with the ohm meter again. Write down the reading that you get. Find the chart for your engine that shows the temperature to resistance conversion. Compare the readings that you get to make sure the sensor is working correctly.

Check out the YouTube video at the bottom of the page for a quick tutorial.

Below is the Temp to resistance chart for the Jeep YJ & XJ. It may work for other fuel injected Jeeps as well.

If you would like a printable copy Click Here

Temperature

Resistance (ohms)

C

F

Min

Max

-40

-40

291,490

381,710

-20

-4

85,850

108,390

-10

14

49,250

61,430

0

32

29,330

35,990

10

50

17,990

21,810

20

68

11,370

13,610

25

77

9,120

10,880

30

86

7,370

8,750

40

104

4,900

5,750

50

122

3,330

3,880

60

140

2,310

2,670

70

158

1,630

1,870

80

176

1,170

1,340

90

194

860

970

100

212

640

720

110

230

480

540

120

248

370

410

Chart information comes from the Chrysler service manual for Jeep YJs and XJs.