PT Cruiser 2006-2007

Mass Air Flow Sensor

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Operation



The Mass Air Flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The Electronic 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 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



  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Disconnect negative battery cable.
  4.  
  5. Remove the air pump assembly.
  6.  
  7. Remove the 2 bracket mounting bolts.
  8.  
  9. Remove the bracket assembly.
  10.  
  11. Disconnect the electrical connector to Mass Air Flow (MAF) sensor.
  12.  
  13. Twist the MAF sideways and remove from bracket.
  14.  
  15. Remove the rubber mounting.
  16.  

To install:

  1. Install the rubber mounting to MAF sensor.
  2.  
  3. Twist the MAF sideways and install to bracket.
  4.  
  5. Connect the electrical connector to the MAF sensor.
  6.  
  7. Install the bracket assembly.
  8.  
  9. Install the 2 bracket mounting bolts.
  10.  
  11. Install the air pump assembly.
  12.  
  13. Connect negative battery cable.
  14.  

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 Mass Air Flow (MAF) sensor parameter. The reading should be between 1,700-3,200 Hz depending on the Engine Coolant Temperature (ECT).
  4.  
  5. Verify that any electrical aftermarket devices are properly connected and grounded.
  6.  
  7. Inspect the harness of the 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
     

  8.  
  9. 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
     

  10.  
  11. Inspect for any contamination or debris on the sensing elements of the MAF sensor.
  12.  
  13. 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.
  14.  
  15. 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 transaxle. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
  16.  
  17. Inspect for a skewed or stuck Engine Coolant Temperature (ECT) sensor.
  18.  
  19. 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.
  20.  

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.

 
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