GM Bonneville/Eighty Eight/LeSabre 1986-1999

Intake Air Temperature Sensor

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The Intake Air Temperature (IAT) sensor is the same as the Manifold Air Temperature (MAT) sensor on earlier models.

The IAT sensor is a thermistor which supplies intake air temperature information to the PCM. The sensor produces high resistance at low temperatures and low resistance at high temperatures. The PCM supplies a 5 volt signal to the sensor and measures the output voltage. The voltage signal will be low when the air is cold and high when the air is hot. The IAT is located in or near the air intake duct.

TESTING



See Figures 1, 2 and 3

  1. If necessary, remove the Intake Air Temperature (IAT) sensor from the vehicle.
  2.  
  3. Connect a digital ohmmeter to the two terminals of the sensor.
  4.  
  5. Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the ambient air. Refer to the temperature vs. resistance chart.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: TESTING the IAT/MAT sensor (which is located in the air cleaner housing) at ambient air temperature

  1. Repeat the test at two other temperature points, heating or cooling the air as necessary with a hair dryer or other suitable tool.
  2.  



Click image to see an enlarged view

Fig. Fig. 2: Measure resistance while using a hair dryer to heat the incoming air. Resistance should fall as the temperature rises

  1. If the sensor does not meet specifications, it must be replaced.
  2.  



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Fig. Fig. 3: IAT sensor circuit

REMOVAL & INSTALLATION



See Figures 4 and 5

  1. Disconnect the negative battery cable.
  2.  
  3. If necessary, remove the air intake cover and filter element.
  4.  
  5. Detach the IAT sensor electrical connector.
  6.  
  7. Grasp and remove the IAT sensor using a twisting and pulling motion.
  8.  



Click image to see an enlarged view

Fig. Fig. 4: The IAT sensor is located in the air cleaner housing on this 1992 vehicle



Click image to see an enlarged view

Fig. Fig. 5: On 1996-98 vehicles, the IAT sensor is mounted in the rear air intake duct

To install:
  1. Position and insert the IAT sensor into the rear air intake duct or air cleaner housing assembly.
  2.  
  3. Attach the sensor electrical connector.
  4.  
  5. If removed, install the air intake cover and filter element.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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