GM Cavalier/Sunbird/Skyhawk/Firenza 1982-1994

Manifold Air Temperature (MAT)/Intake Air Temperature (IAT) Sensor

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OPERATION



See Figure 1

The MAT or IAT sensor (as equipped), is a thermistor (resistor which changes value based on temperature) mounted either in the air intake snorkel or the manifold (depending on the application). Low intake air temperatures produce a high resistance - 100,000 ohms at -40°F (-40°C), while high temperatures cause low resistance - 70 ohms at 266°F (130°C).

The control module provides a 5 volt reference signal to the sensor through a resistor in the module and measures the voltage. The voltage will be high when the air is cold and low when the air is hot. By measuring the voltage, the control module knows the intake/manifold air temperature.



Click image to see an enlarged view

Fig. Fig. 1: View of the MAT/IAT sensor and electrical connector - 1995 2.3L shown

The air temperature signal is used by the control module to delay EGR until the temperature reaches approximately 40°F (5°C). The control module also uses the signal to retard ignition timing during high air temperatures.

TESTING



See Figure 2

  1. Disconnect the MAT/IAT sensor.
  2.  
  3. Connect an ohmmeter between the sensor terminals.
  4.  
  5. Measure the resistance with the engine off and cool. Then measure with the engine running and warmed up. Compare the resistance values obtained with the chart.
  6.  
  7. Replace the sensor if the readings are incorrect.
  8.  



Click image to see an enlarged view

Fig. Fig. 2: MAT/IAT sensor value chart

REMOVAL & INSTALLATION



See Figure 3

The MAT/IAT sensor is usually located in the air cleaner assembly or in the top of the intake manifold between the runners.

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the sensor electrical connector.
  4.  
  5. If necessary, remove the air cleaner assembly cover to gain access to the sensor.
  6.  



Click image to see an enlarged view

Fig. Fig. 3: On the 1988 2.0L (VIN K) engine, the MAT sensor is mounted in the air cleaner assembly

  1. Carefully remove the sensor and retainer (if equipped).
  2.  
  3. Installation is the reverse of the removal procedure.
  4.  

 
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