Infiniti Car 1998-05

Mass Air Flow (MAF) Sensor

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Operation



The mass air flow sensor measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to the hot film as the air flow increases. This maintains the temperature of the hot film. The ECM detects the air flow by means of this current change.

The mass air flow sensor measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to the hot film as the air flow increases. This maintains the temperature of the hot film. The ECM detects the air flow by means of this current change.

The mass air flow sensor measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to the hot film as the air flow increases. This maintains the temperature of the hot film. The ECM detects the air flow by means of this current change.

The mass air flow sensor measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to the hot film as the air flow increases. This maintains the temperature of the hot film. The ECM detects the air flow by means of this current change.

The mass air flow sensor measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to the hot film as the air flow increases. This maintains the temperature of the hot film. The ECM detects the air flow by means of this current change.

Testing





Click image to see an enlarged view

Fig. The mass air flow sensor-2.0L engine

  1. Turn the ignition switch to the on position.
  2.  
  3. Start the engine and warm it up to the normal operating temperature.
  4.  
  5. Check the voltage between terminal 4 and ground.

    With the ignition switch on, the voltage should read less than 1.0 volts.
     
    At idle, the voltage should be 1.3-1.7 volts.
     
    At 2500RPM, the voltage should be 1.8-2.4 volts.
     
    From idle to about 4000 RPM, the voltage should be 1.3-1.7 to approximately 4.0 volts.
     

  6.  
  7. If the voltage is out of specification, disconnect the mass air flow sensor harness connector and connect it again. Repeat the above check.
  8.  
  9. If the results aren-t obtained, remove the mass air flow sensor from the air duct and check the hot film for damage or dust.
  10.  

  1. Start the engine and warm it up to the normal operating temperature.
  2.  
  3. Check the voltage between the ECM terminal 51 (sensor signal) and ground.

    If the ignition switch is on but the engine is stopped, the voltage should read approximately 0.4 volts.
     
    At idle, the voltage should be 0.9-1.2 volts.
     
    At 2500 RPM, the voltage should be 1.5-1.9 volts.
     
    From idle to about 4000 RPM, the voltage should be 0.9-1.2 to approximately 2.4 volts.
     

  4.  
  5. If the voltage is out of specification, disconnect the mass air flow sensor harness connector and connect it again.
  6.  
  7. Also check for crushed air ducts, malfunctioning seals on the cleaner element, uneven dirt on the element, or other improper specifications of the intake air system.
  8.  
  9. If everything checks out to be in proper working order, replace the mass air flow sensor.
  10.  

  1. Turn the ignition switch to the on position.
  2.  
  3. Start the engine and warm it up to the normal operating temperature.
  4.  
  5. Check the voltage between terminal 4 and ground.

    With the ignition on, the voltage should read less than 1.0 volts.
     
    At idle, the voltage should read 1.0-1.7 volts.
     
    Between idle and 4000 RPM, the voltage should be 1.0-1.7 and approximately 4.0 volts. Check for a linear voltage rise in response to an increase in engine speed to about 4000 RPM.
     

  6.  
  7. If these voltages are not read under those conditions, remove the mass air flow sensor from the air duct and check the hot film for damage or dust. Replace it and conduct the above test again.
  8.  

  1. Turn the ignition switch to the on position.
  2.  
  3. Start the engine and warm it up to the normal operating temperature.
  4.  
  5. Check the voltage between terminal 4 and ground.

    With the ignition on, the voltage should read less than 1.0 volts.
     
    At idle, the voltage should read 1.0-1.7 volts.
     
    Between idle and 4000 RPM, the voltage should be 1.0-1.7 and approximately 4.0 volts. Check for a linear voltage rise in response to an increase in engine speed to about 4000 RPM.
     

  6.  
  7. If these voltages are not read under those conditions, remove the mass air flow sensor from the air duct and check the hot film for damage or dust. Replace it and conduct the above test again.
  8.  



Click image to see an enlarged view

Fig. The mass air flow sensor and connector

  1. Turn the ignition switch to the on position.
  2.  
  3. Start the engine and warm it up to the normal operating temperature.
  4.  
  5. Check the voltage between terminal 4 and ground.

    With the ignition on, the voltage should read less than 1.0 volts.
     
    At idle, the voltage should read 1.0-1.7 volts.
     
    For the 4.1L engine, at 2000 RPM, the voltage should be approximately 2.1 volts.
     
    Between idle and 4000 RPM, the voltage should be 1.0-1.7 and approximately 4.0 volts. Check for a linear voltage rise in response to an increase in engine speed to about 4000 RPM.
     

  6.  
  7. If these voltages are not read under those conditions, remove the mass air flow sensor from the air duct and check the hot film for damage or dust. Replace it and conduct the above test again.
  8.  

 
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