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.



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Fig. Fig. 1: Intake Air Temperature (IAT) sensor-diesel engines

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) and Engine Coolant Temperature (ECT) sensor wiring diagram



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Fig. Fig. 3: IAT sensor temperature vs. resistance values

REMOVAL & INSTALLATION



  1. Unplug the sensor electrical connection.
  2.  
  3. Loosen and remove the sensor from the vehicle.
  4.  
  5. Installation is the reverse of removal.
  6.  

 
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