HHR 2006-2008

Mass Air Flow Sensor

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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



2.0L Engines


Click image to see an enlarged view

Fig. Intake Air Temperature (IAT)/Mass Air Flow (MAF) sensor location-2.0L engine

  1. Disconnect the Intake Air Temperature (IAT)/Mass Air Flow (MAF) sensor harness connector.
  2.  
  3. Remove the IAT/MAF sensor bolt.
  4.  
  5. While twisting the IAT/MAF sensor (3), pull the sensor from the engine.
  6.  

To install:

  1. Press the IAT/MAF sensor (3) into the engine.
  2.  
  3. Install the IAT/MAF sensor bolt. Tighten the bolt to 89 inch lbs. (10 Nm).
  4.  
  5. Connect the IAT/MAF sensor harness connector.
  6.  

2.4L Engine


Click image to see an enlarged view

Fig. Mass Air Flow (MAF)/Intake Air Temperature (IAT) sensor location-2.4L engine

  1. Disconnect the engine 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. Install the MAF/IAT sensor.
  2.  
  3. Install the MAF/IAT sensor screws. Tighten the screws to 5 inch lbs. (0.6 Nm).
  4.  
  5. Connect the engine harness electrical connector to the MAF/IAT sensor.
  6.  

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


Click image to see an enlarged view

Fig. Mass Air Flow (MAF)/Intake Air Temperature (IAT) connector end view-2.0L engine, 2.2L, & 2.4L engines


NOTE
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. 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.
  4.  
  5. With 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.
  6.  
  7. With the ignition ON, test for 4.8-5.2 volts between the signal circuit terminal A and ground:
    1. 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.
    2.  
    3. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    4.  

  8.  

 
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