GM Lumina/Grand Prix/Cutlass Supreme/Regal 1988-1996

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

Print

OPERATION



The Intake Air Temperature (IAT) sensor, also known as the Manifold Air Temperature (MAT) sensor, is a thermistor which supplies manifold air temperature information to the ECM. The MAT sensor produces high resistance (100,000 ohms at 40ºF/40ºC) at low temperatures and low resistance of 70 ohms at 266ºF (130ºC) at high temperatures. The ECM supplies a 5 volt signal to the MAT sensor and measures MAT sensor output voltage. The voltage signal will be high when the 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. The IAT sensor is usually mounted in the air cleaner housing or in the air intake duct.

TESTING



See Figures 1, 2, 3 and 4

Click image to see an enlarged view

Fig. Fig. 1: MAT sensor temperature vs. resistance values



Click image to see an enlarged view

Fig. Fig. 2: MAT sensor wiring digram - 1988-93 vehicles



Click image to see an enlarged view

Fig. Fig. 3: MAT sensor wiring diagram - 1994-96 3.1L engine



Click image to see an enlarged view

Fig. Fig. 4: Intake Air Temperature (IAT) sensor wiring diagram - 1994-96 3.4L and 3.8L engines

  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.  

REMOVAL & INSTALLATION



See Figures 5, 6 and 7

Click image to see an enlarged view

Fig. Fig. 5: On the 2.2L engine, the IAT sensor is mounted the the air cleaner duct



Click image to see an enlarged view

Fig. Fig. 6: The IAT sensor is mounted in the rear intake duct on this 1996 3.8L engine



Click image to see an enlarged view

Fig. Fig. 7: Detach the connector, then remove the IAT sensor-1992 3.1L engine shown

  1. Disconnect the negative battery cable.
  2.  
  3. If necessary for access, remove the air cleaner cover and filter element.
  4.  
  5. Detach the sensor electrical connector.
  6.  
  7. If equipped, unfasten the retaining clamp or clip from the sensor.
  8.  
  9. Carefully remove the sensor. The sensor is either threaded or snaps into place.
  10.  

To install:
  1. Coat the sensor threads with sealant 1052080 or equivalent.
  2.  
  3. Install the sensor. If equipped, secure with the clamp or clip, as applicable.
  4.  
  5. Attach the electrical connector.
  6.  
  7. If equipped, install the air cleaner filter element and cover.
  8.  
  9. Connect the negative battery cable.
  10.  

 
label.common.footer.alt.autozoneLogo