Aura, Outlook 2007

Mass Air Flow & Intake Air Temperature Sensor

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Operation



The manifold absolute pressure (MAP) and the intake air temperature (IAT) sensor are an integrated sensor. The IAT sensor is a variable resistor that measures the temperature of the air entering the engine intake manifold. The powertrain control module (PCM) supplies 5 volts to the IAT sensor signal circuit and a ground for the IAT sensor low reference circuit. When the sensor is cold the resistance is greater. This results in a greater voltage on the signal circuit that is interpreted by the PCM as a colder IAT. As the sensor becomes warmer the resistance decreases. This results in a lesser voltage on the IAT signal circuit that is interpreted by the PCM as a warmer IAT.

Removal & Installation



2.4L Engine
  1. Disconnect the engine wiring harness electrical connector from the Mass Air Flow (MAF)/Intake Air Temperature (IAT) sensor.
  2.  
  3. Remove the MAF/IAT sensor screws.
  4.  
  5. Remove the MAF/IAT sensor.
  6.  

To install:

  1. Installation is the reverse of removal.
  2.  

3.5L Engines
  1. Remove the air cleaner outlet duct.
  2.  
  3. Disconnect the engine wiring harness electrical connector from the Mass Air Flow (MAF)/Intake Air Temperature (IAT) sensor.
  4.  
  5. Remove the MAF/IAT sensor screws.
  6.  
  7. Remove the MAF/IAT sensor and seal.
  8.  

To install:

  1. Installation is the reverse of removal. Install a new sensor seal.
  2.  

3.6L Engines
  1. Remove the air cleaner outlet duct.
  2.  
  3. Disconnect the engine wiring harness electrical connector from the Mass Air Flow (MAF)/Intake Air Temperature (IAT) sensor.
  4.  
  5. Remove the MAF/IAT sensor screws.
  6.  
  7. Remove the MAF/IAT sensor and seal.
  8.  

To install:

  1. Installation is the reverse of removal. Install a new sensor seal.
  2.  

Testing



2.4L Engine


Click image to see an enlarged view

Fig. Mass Air Flow (MAF)/Intake Air Temperature (IAT) sensor-2.4L engine terminals (A) MAF Sensor Signal (B) Ground (C) Ignition 1 Voltage (D) Low Reference (E) IAT Sensor Signal

  1. Verify the integrity of the air induction system by inspecting for loose or improper installation. Water in the system.
  2.  
  3. Turn the ignition OFF, disconnect the MAF/IAT harness connector at the MAF/IAT sensor.
  4.  
  5. Turn the ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  6.  
  7. Turn the ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  8.  
  9. Turn the ignition ON, test for 4.8-5.2 volts between the signal circuit terminal A and ground. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  10.  
  11. Connect a Variable Signal Generator such as J 38522 to the vehicle.
  12.  
  13. To determine if the ECM can properly process the MAF sensor frequency signal, connect the J 38522 to the vehicle as follows:
  14.  
  15. Turn OFF the ignition.
  16.  
  17. Connect the battery voltage supply, and ground the black lead.
  18.  
  19. Connect the red lead to the signal circuit of the MAF sensor.
  20.  
  21. Set the duty cycle switch to Normal.
  22.  
  23. Set the Frequency switch to 5 K.
  24.  
  25. Set the signal switch to 5 volts.
  26.  
  27. Start the engine.
  28.  
  29. Observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz. If the MAF Sensor parameter is not within the specified range, replace the ECM. If the MAF Sensor parameter is within the specified range, replace the MAF sensor.
  30.  

3.5L & 3.6L Engines
  1. Verify the integrity of the entire air induction system by inspecting for the following:

    Any damaged components
     
    Loose or improper installation
     
    An air flow restriction
     
    Any vacuum leaks
     
    Water intrusion
     
    In cold climates, inspect for any snow or ice buildup
     

  2.  
  3. Turn the ignition OFF, disconnect the MAF/IAT harness connector at the MAF/IAT sensor.
  4.  
  5. Turn the ignition OFF for 90 seconds, test for less than 5.0 ohms of resistance between the ground circuit terminal C and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  6.  
  7. Turn the ignition ON, verify that a test lamp illuminates between the ignition circuit terminal B and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  8.  
  9. Turn the ignition ON, test for 4.8-5.2 volts between the signal circuit terminal A and ground. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  10.  
  11. Connect a variable signal generator such as J 38522 to the vehicle.
  12.  
  13. To determine if the ECM can properly process the MAF sensor frequency signal, connect a variable signal generator such as J 38522 as follows:
    1. Turn OFF the ignition.
    2.  
    3. Connect the battery voltage supply, and ground the black lead.
    4.  
    5. Connect the red lead to the signal circuit terminal A.
    6.  
    7. Set the duty cycle switch to Normal.
    8.  
    9. Set the Frequency switch to 5 K.
    10.  
    11. Set the signal switch to 5 volts.
    12.  

  14.  
  15. Start the engine. Observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz. If the MAF Sensor parameter is not within the specified range, replace the ECM. If the MAF Sensor parameter is within the specified range, replace the MAF sensor.

    Click image to see an enlarged view

    Fig. Mass Air Flow (MAF)/Intake Air Temperature (IAT) sensor terminals-3.5L and 3.6L engines (A) MAF Sensor Signal (B) Ignition 1 Voltage (C) Ground (D) IAT Sensor Signal (E) Low Reference

  16.  

 
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