Intake Air Temperature(IAT) - Testing & Replacing for 99+


xeroinfinity
01-22-2007, 03:57 PM
Intake Air Temperature (IAT)- Test & Replacing

The IAT is a thermistor, a resistor that varies the value of resistance accornding to temperature changes. The change in resistance will directly affect teh voltsge signal from teh sensor to the PCM.

As the sensor temp. increases, the resistance valvues will decrease. As the sensor temps. decrease teh resistance will increase.

* Performing this test will set a diagnostic trouble code and will illuminate the check engine light. Clear DTC after performing tests and or repairs.

- The IAT is located in the air intake tube between the air filter housing and the TB.
- 4 cyl (http://i28.photobucket.com/albums/c242/xeroinfinity/11X17RW24/IAT4cyl.jpg)
- V6 (http://i28.photobucket.com/albums/c242/xeroinfinity/11X17RW24/IATV6.jpg)

- Check the terminals in the connctor and the wires leading to the sensor for looseness of breaks.
- Repiar if needed.

http://i28.photobucket.com/albums/c242/xeroinfinity/11X17RW24/IATtermincont.jpg
- First check the voltage supply and ground cicuits from the PCM.
- Disconnect the elec. connector from the IAT sensor.
- Connect the positive lead to the TAN wire and the ground lead to the black or gray wire.
- Turn the key on, should be approx 5volts.
- If the voltage was incorrect, check the wiring from the PCM to the Sensor. If the cicuits are good, have the PCM checked by a dealer or other qualified service deprt.

- Resistance Values Chart -
http://i28.photobucket.com/albums/c242/xeroinfinity/11X17RW24/tempresistancevalues.jpg

- With the Ignition off, disconnect the connector from the IAT.
- Using an Ohmmeter measure the resistance between the sensor terminals while it is cold, 50-80deg F.

- Reconnect the connector, start the engine and allow to warm up completely, 180-200 deg F.

- Disconnect the sensor and check the resistance again.
- Compare the two values to the resistance chart.

- If the values are incorrect, replace the sensor.

- Replacing the sensor -

- Disconnect the sensor connector.
- Carefull remove the IAT from the air duct.
- Install in reverse.

Hope this helps!

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