GM Full Size Vans 1987-1997 Repair Guide

Intake Air Temperature (IAT) Sensor

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OPERATION



See Figure 1

the Intake Air Temperature (IAT) Sensor is a thermistor which changes value based on the temperature of the air entering the engine. Low temperature produces a high resistance, while a high temperature causes a low resistance. The ECM supplies a 5 volt signal to the sensor through a resistor in the ECM and measures the voltage. The voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the ECM calculates the incoming air temperature.

the IAT sensor signal is used to adjust spark timing according to incoming air density.



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Fig. Fig. 1: Intake Air Temperature (IAT) sensor

TESTING



See Figures 2 and 3

  1. Remove the Intake Air Temperature (IAT) sensor.
  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 illustration.
  6.  
  7. Repeat the test at two other temperature points, heating or cooling the air as necessary with a hair dryer or other suitable tool.
  8.  
  9. If the sensor does not meet specification, it must be replaced.
  10.  



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Fig. Fig. 2: Intake Air Temperature (IAT) sensor wiring diagram



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Fig. Fig. 3: Intake Air Temperature (IAT) sensor temperature vs. resistance values

REMOVAL & INSTALLATION



See Figures 4 and 5

  1. Disconnect the negative battery cable.
  2.  
  3. Disengage the sensor electrical connection.
  4.  
  5. Loosen and remove the IAT sensor.
  6.  
  7. Installation is the reverse of removal.
  8.  



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Fig. Fig. 4: Unplug the IAT sensor electrical connection



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Fig. Fig. 5: Grasp the IAT sensor and pull it from the air duct

 
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