LaCrosse 2006-2007

Mass Air Flow Sensor

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Fig. Intake Air Temperature (IAT)/Mass Air Flow (MAF) sensor location-3.6L engine



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Fig. Intake Air Temperature (IAT)/Mass Air Flow (MAF) sensor location-3.8L engine

Operation



The Mass Air Flow (MAF) sensor is integrated with the Intake Air Temperature (IAT) sensor. The MAF sensor is an air flow meter that measures the amount of air entering the engine. The Engine Control Module (ECM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF/IAT sensor has the following circuits:



An ignition 1 voltage circuit
 
A ground circuit
 
A MAF sensor signal circuit
 
An IAT sensor signal circuit
 
A low reference circuit
 

The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies in a range of near 1,700 Hertz at idle to near 9,500 Hertz at maximum engine load.

Removal & Installation



3.6L Engine
  1. Turn the ignition OFF.
  2.  
  3. Remove the Intake Air Temperature (IAT)/Mass Air Flow (MAF) electrical connector.
  4.  
  5. Remove the air cleaner intake duct.
  6.  
  7. Remove the IAT/MAF sensor fasteners.
  8.  
  9. Remove the IAT/MAF sensor and the IAT/MAF sensor seal.

    Click image to see an enlarged view

    Fig. Intake Air Temperature (IAT)/Mass Air Flow (MAF) sensor location-3.6L engine

  10.  

To install:

  1. Install the new IAT/MAF sensor seal and the IAT/MAF sensor.
  2.  
  3. Install the IAT/MAF sensor screws. Tighten the IAT/MAF sensor screws to 35 inch lbs. (4 Nm).
  4.  
  5. Install the air cleaner intake duct.
  6.  
  7. Install the IAT/MAF electrical connector.
  8.  

3.8L Engine
  1. Remove the fuel injector sight shield.
    NOTE
    The Intake Air Temperature (IAT) sensor and the Mass Air Flow (MAF) sensor are combined as one sensor.

  2.  
  3. Disconnect the MAF/IAT sensor electrical connector (2).
  4.  
  5. Loosen the air cleaner intake duct clamps.
  6.  
  7. Remove the air cleaner intake duct from the air cleaner housing cover and the throttle body assembly.
  8.  
  9. Remove the MAF/IAT sensor from the air cleaner intake duct.

    Click image to see an enlarged view

    Fig. Intake Air Temperature (IAT)/Mass Air Flow (MAF) sensor location-3.8L engine

  10.  

To install:

  1. Install the MAF/IAT sensor to the air cleaner intake duct.
  2.  
  3. Install the air cleaner intake duct to the air cleaner housing cover and the throttle body assembly.
  4.  
  5. Tighten the air cleaner intake duct clamp screws. Tighten the duct clamps to 27 inch lbs. (3 Nm).
  6.  
  7. Connect the MAF/IAT sensor electrical connector.
  8.  
  9. Install the fuel injector sight shield.
  10.  

Testing



  1. Verify the integrity of the air induction system by inspecting for the following conditions:

    Damaged components
     
    Loose or improper installation
     
    An air flow restriction
     
    Any vacuum leak
     
    Water intrusion
     

  2.  
  3. With the engine running, observe the scan tool MAF sensor parameter. The reading should be between 1,700-3,200 Hz depending on the Engine Coolant Temperature (ECT).
  4.  
  5. A Wide Open Throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 2-6 g/s at idle to greater than 100 g/s at the time of the 1-2 shift.
  6.  
  7. Verify that any electrical aftermarket devices are properly connected and grounded.
  8.  

Circuit Testing


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Fig. Mass Air Flow (MAF)/Intake Air Temperature (IAT) connector end view-3.6L engine



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Fig. Mass Air Flow (MAF)/Intake Air Temperature (IAT) connector end view-3.8L engine

  1. Inspect the harness of the Mass Air Flow (MAF) sensor to verify that it is not routed too close to the following components:

    Any aftermarket accessories
     
    The secondary ignition wires or coils
     
    Any solenoids
     
    Any relays
     
    Any motors
     

  2.  
  3. A low minimum air rate through the sensor bore at idle or during deceleration may cause a DTC to set. Inspect for the following conditions:

    Any deposits on the throttle plate or in the throttle bore
     
    Any vacuum leak downstream of the MAF sensor
     

  4.  
  5. Inspect for any contamination or debris on the sensing elements of the MAF sensor.
  6.  
  7. Inspect the air induction system for any water intrusion. Any water that reaches the MAF sensor will skew the sensor and may cause a DTC to set.
  8.  
  9. A Wide Open Throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 3-10 g/s at idle to 150 g/s or more at the time of the 1 to 2 shift of the transmission. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
  10.  
  11. Inspect for a skewed or stuck Engine Coolant Temperature (ECT) sensor.
  12.  
  13. Test for a high resistance of 15 ohms or more on the ignition 1 voltage circuit. This may cause a DTC to set. A high resistance may also cause a drivability concern before a DTC sets.
  14.  

The Barometric Pressure (BARO) sensor that is used in order to calculate the predicted mass air flow value is initially based on the Manifold Absolute Pressure (MAP) sensor at key ON. When the engine is running, the BARO value is continually updated near WOT. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate and may result in a no start condition. The value shown for the MAP sensor parameter varies with the altitude. With the ignition ON and the engine OFF, 101 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 1,000 feet (305 meters) of altitude.


NOTE
For the following tests, all electrical components and accessories must be turned OFF, and allowed to power down.

  1. With the ignition OFF, disconnect the MAF/IAT harness connector at the MAF/IAT sensor.
  2.  
  3. With the ignition ON, verify that a test lamp illuminates between the ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  4.  
  5. With the ignition ON, test for 4.8-5.2 volts between the signal circuit terminal and ground:
    1. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance.
    2.  
    3. If greater than the specified range, test the signal circuit for a short to voltage.
    4.  

  6.  
  7. If all circuits test normal, replace the MAF sensor.
  8.  

 
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