Chrysler Full-Size Trucks 1997-2000 Repair Guide

Intake Air Temperature (IAT) Sensor

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OPERATION



The two-wire Intake Manifold Air Temperature (IAT) sensor is installed in the intake manifold with the sensor element extending into the air stream.

  1. This is a Negative Thermal Coefficient (NTC), meaning that as the manifold air temperature increases, the resistance (voltage) in the sensor decreases, and vice-versa.
  2.  
  3. The IAT sensor provides an input voltage to the PCM, indicating the density of the air entering the intake manifold based on intake manifold air temperature. When the ignition is turned ON , a 5-volt power circuit is supplied to the sensor from the PCM. The sensor is grounded at the PCM through a low-noise, sensor-return circuit.
  4.  
  5. The PCM uses this input to determine:

    Injector pulse-width (air: fuel ratio)
     
    Ignition timing (to prevent spark knock)
     

  6.  



Click image to see an enlarged view

Fig. IAT sensor installed in the intake manifold of a 5.2L engine. Others similar

TESTING



  1. Be sure the ignition is OFF .
  2.  
  3. Disconnect the connector at the IAT sensor.
  4.  
  5. Check resistance across the sensor terminals. Using an input impedance (digital) VOM is recommended.
  6.  
  7. Resistance will vary with temperature, but should be about 18 kilo-ohms at 50ºF (10ºC), decreasing rapidly as temperature increases to about 1kilo-ohms at 176ºF (80ºC) which is near engine operating temperature. If the measured resistance is at or near zero (shorted) or at or near infinity (open), replace the sensor.
  8.  
  9. To test the harness, proceed as follows:
    1. Shut the ignition OFF and disconnect the battery negative cable.
    2.  
    3. Unplug the PCM, test the harness between the proper PCM connector terminal and the sensor connector. Also check the harness between the proper PCM connector terminal and the sensor connector. If resistance is more than 1 ohm, repair the wiring harness.
    4.  

  10.  


WARNING
Testing the wiring harness with the PCM still connected can cause serious damage to the processor. ALWAYS disconnect the PCM before testing the wiring harness, unless instructed otherwise.

  1. Connect the negative battery cable.
  2.  



Click image to see an enlarged view

Fig. Testing the IAT sensor with an ohmmeter connected across the two sensor terminals



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Fig. IAT sensor circuit



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Fig. IAT sensor's electrical connector terminal identification: (1) BK/LB; (2) BK/RD

REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the electrical connector from the sensor.
  4.  
  5. Unscrew the sensor from the intake manifold.
  6.  

To install:

  1. Install the sensor into the intake manifold and tighten it to 20 ft. lbs. (28 Nm).
  2.  
  3. Plug the connector into the sensor.
  4.  
  5. Connect the negative battery cable.
  6.  



Click image to see an enlarged view

Fig. IAT sensor location-2.5L engine shown

 
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