GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

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.

Removal and installation of the MAT/IAT sensor is covered in Engine & Engine Overhaul of this information. Please refer there for further information.

TESTING



See Figure 2

Refer to Engine Coolant Temperature Sensor testing.



Click image to see an enlarged view

Fig. Fig. 2: Testing the Intake Air Temprature sensor resistance

REMOVAL & INSTALLATIONExcept 3.1L Engine



See Figures 3 and 4

  1. Disconnect the negative battery cable.
  2.  
  3. Make sure ignition switch is in the OFF position.
  4.  
  5. Detach the electrical connector from the IAT sensor.
  6.  



Click image to see an enlarged view

Fig. Fig. 3: Some IAT sensor are located in the air cleaner housing-2.3L (VIN D) engine

  1. Carefully remove the sensor from the intake manifold or air cleaner housing.
  2.  



Click image to see an enlarged view

Fig. Fig. 4: Remove the clamp retaining the IAT sensor

To install:
  1. Coat the sensor threads with sealer 9985253 or equivalent, then install the IAT sensor in the intake manifold.
  2.  
  3. Tighten the sensor to 6 ft. lbs. (8 Nm)
  4.  
  5. Attach the electrical connector to the sensor.
  6.  
  7. Connect the negative battery cable.
  8.  

3.1L Engine

The IAT sensor on the 3.1L engine is located in the air cleaner.

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the sensor electrical connector.
  4.  
  5. Unfasten the retaining clamp, then remove the sensors.
  6.  

To install:
  1. Install the sensors, then secure using the retaining clamps.
  2.  
  3. Attach the sensor electrical connector, then connect the negative battery cable.
  4.  

 
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