Mitsubishi Car 1999-05

Mass Air Flow (MAF) Sensor

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Operation



The Mass Air Flow (MAF) sensor directly measures the mass of air being drawn into the engine. The sensor output is used to calculate injector pulse width. The MAF sensor is what is referred to as a "hot-wire sensor". The sensor uses a thin platinum wire filament, wound on a ceramic bobbin and coated with glass, that is heated to 417°F (200°C) above the ambient air temperature and subjected to the intake airflow stream. A "cold-wire" is used inside the MAF sensor to determine the ambient air temperature.

Battery voltage, a reference signal, and a ground signal from the PCM are supplied to the MAF sensor. The sensor returns a signal proportionate to the current flow required to keep the "hot-wire" at the required temperature. The increased airflow across the "hot-wire" acts as a cooling fan, lowering the resistance and requiring more current to maintain the temperature of the wire. The increased current is measured by the voltage in the circuit, as current increases, voltage increases. As the airflow increases the signal return voltage of a normally operating MAF sensor will increase.

A 5-volt power is applied to the Mass Air Flow (MAF) Sensor output terminal from the ECM/PCM. The sensor generates a pulse signal when the output terminal and ground are opened/closed (opened/short).

A 5-volt power is applied to the Mass Air Flow (MAF) Sensor output terminal from the ECM/PCM. The sensor generates a pulse signal when the output terminal and ground are opened/closed (opened/short).

A 5-volt power is applied to the Mass Air Flow (MAF) Sensor output terminal from the ECM/PCM. The sensor generates a pulse signal when the output terminal and ground are opened/closed (opened/short).

A 5-volt power is applied to the Mass Air Flow (MAF) Sensor output terminal from the ECM/PCM. The sensor generates a pulse signal when the output terminal and ground are opened/closed (opened/short).

A 5-volt power is applied to the Mass Air Flow (MAF) Sensor output terminal from the ECM/PCM. The sensor generates a pulse signal when the output terminal and ground are opened/closed (opened/short).

A 5-volt power is applied to the Mass Air Flow (MAF) Sensor output terminal from the ECM/PCM. The sensor generates a pulse signal when the output terminal and ground are opened/closed (opened/short).

Removal & Installation





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Fig. Release the retaining clips from the air cleaner housing



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Fig. Unplug the MAF sensor connector



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Fig. Detach the breather hose from the air inlet tube



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Fig. Loosen the clamp on the air outlet tube at the throttle body . . .



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Fig. . . . then remove the air outlet tube and upper housing from the lower housing



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Fig. Loosen the hose clamp retaining screw . . .



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Fig. . . . then slide the outlet hose off of the MAF sensor



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Fig. Remove the four sensor-to-air cleaner housing retaining nuts . . .



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Fig. . . . then remove the MAF sensor from the air cleaner cover

  1. Disconnect the negative battery cable.
  2.  
  3. Release the retaining clips from the air cleaner housing.
  4.  
  5. Loosen the clamp on the air outlet tube at the throttle body.
  6.  
  7. Remove the breather hose and detach the connector from the MAF sensor.
  8.  
  9. Remove the air outlet tube and upper housing from the lower housing.
  10.  
  11. Loosen the hose clamp and slide the outlet hose off of the MAF sensor.
  12.  
  13. Remove the four sensor-to-air cleaner housing retaining nuts.
  14.  
  15. Remove the sensor from the air cleaner upper housing.
  16.  


NOTE
Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  1. Installation is the reverse of the removal procedure.
  2.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

Testing



  1. Using a multimeter, check for voltage by backprobing the MAF sensor connector.
  2.  
  3. With the ignition key ON , and the engine OFF , verify that there is at least 10.5 volts between the BATT and GND terminals of the MAF sensor connector. If voltage is not within specification, check power and ground circuits and repair as necessary.
  4.  
  5. With the ignition key ON , and the engine ON , verify that there is at least 4.5 volts between the SIG and GND terminals of the MAF sensor connector. If voltage is not within specification, check power and ground circuits and repair as necessary.
  6.  
  7. With the ignition key ON , and the engine ON , check voltage between GND and SIG RTN terminals. Voltage should be approximately 0.34-1.96 volts. If voltage is not within specification, the sensor may be faulty.
  8.  

  1. Connect a suitable scan tool to read data.
  2.  
  3. Start the engine and run at idle. Warm up the engine to normal operating temperature: 176° to 205°F.
    1. The standard value during idling should be 10 Hz or more.
    2.  
    3. When the engine is revved, the frequency should increase according to the increase in engine speed.
    4.  

  4.  
  5. If the checks above do not meet the specification, disconnect the sensor connector and measure at the harness side.
  6.  
  7. Turn the ignition switch to "ON" position, and measure the voltage between terminal 4 and ground. Voltage should be battery positive voltage.
  8.  
  9. Turn the ignition switch to "LOCK" (OFF) position.
  10.  
  11. If not within specifications, check and repair/replace the connector(s), harness wire between MFI relay and/or the MFI relay.
  12.  
  13. If within specifications, disconnect the sensor connector and measure at the harness side.
  14.  
  15. Turn the ignition switch to "ON" position and measure the voltage between terminal 3 and ground. Voltage should be between 4.8 and 5.2 volts.
  16.  
  17. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 5 and ground. Resistance be less than 2 ohm.
  18.  
  19. If all checks above meet the specifications, replace the sensor.
  20.  
  21. If any check above does not meet the specifications, replace the ECM/PCM.
  22.  

  1. Connect a suitable scan tool to read data.
  2.  
  3. Start the engine and run at idle. Warm up the engine to normal operating temperature: 176° to 205°F.
    1. The standard value during idling should be 10 Hz or more.
    2.  
    3. When the engine is revved, the frequency should increase according to the increase in engine speed.
    4.  

  4.  
  5. If the checks above do not meet the specification, disconnect the sensor connector and measure at the harness side.
  6.  
  7. Turn the ignition switch to "ON" position, and measure the voltage between terminal 4 and ground. Voltage should be battery positive voltage.
  8.  
  9. Turn the ignition switch to "LOCK" (OFF) position.
  10.  
  11. If not within specifications, check and repair/replace the connector(s), harness wire between MFI relay and/or the MFI relay.
  12.  
  13. If within specifications, disconnect the sensor connector and measure at the harness side.
  14.  
  15. Turn the ignition switch to "ON" position and measure the voltage between terminal 3 and ground. Voltage should be between 4.8 and 5.2 volts.
  16.  
  17. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 5 and ground. Resistance be less than 2 ohm.
  18.  
  19. If all checks above meet the specifications, replace the sensor.
  20.  
  21. If any check above does not meet the specifications, replace the ECM/PCM.
  22.  

  1. Connect a suitable scan tool to read data.
  2.  
  3. Start the engine and run at idle. Warm up the engine to normal operating temperature: 176° to 205°F.
    1. The standard value during idling should be 10 Hz or more.
    2.  
    3. When the engine is revved, the frequency should increase according to the increase in engine speed.
    4.  

  4.  
  5. If the checks above do not meet the specification, disconnect the sensor connector and measure at the harness side.
  6.  
  7. Turn the ignition switch to "ON" position, and measure the voltage between terminal 4 and ground. Voltage should be battery positive voltage.
  8.  
  9. Turn the ignition switch to "LOCK" (OFF) position.
  10.  
  11. If not within specifications, check and repair/replace the connector(s), harness wire between MFI relay and/or the MFI relay.
  12.  
  13. If within specifications, disconnect the sensor connector and measure at the harness side.
  14.  
  15. Turn the ignition switch to "ON" position and measure the voltage between terminal 3 and ground. Voltage should be between 4.8 and 5.2 volts.
  16.  
  17. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 5 and ground. Resistance be less than 2 ohm.
  18.  
  19. If all checks above meet the specifications, replace the sensor.
  20.  
  21. If any check above does not meet the specifications, replace the ECM/PCM.
  22.  

  1. Connect a suitable scan tool to read data.
  2.  
  3. Start the engine and run at idle. Warm up the engine to normal operating temperature: 176° to 205°F.
    1. The standard value during idling should be 10 Hz or more.
    2.  
    3. When the engine is revved, the frequency should increase according to the increase in engine speed.
    4.  

  4.  
  5. If the checks above do not meet the specification, disconnect the sensor connector and measure at the harness side.
  6.  
  7. Turn the ignition switch to "ON" position, and measure the voltage between terminal 4 and ground. Voltage should be battery positive voltage.
  8.  
  9. Turn the ignition switch to "LOCK" (OFF) position.
  10.  
  11. If not within specifications, check and repair/replace the connector(s), harness wire between MFI relay and/or the MFI relay.
  12.  
  13. If within specifications, disconnect the sensor connector and measure at the harness side.
  14.  
  15. Turn the ignition switch to "ON" position and measure the voltage between terminal 3 and ground. Voltage should be between 4.8 and 5.2 volts.
  16.  
  17. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 5 and ground. Resistance be less than 2 ohm.
  18.  
  19. If all checks above meet the specifications, replace the sensor.
  20.  
  21. If any check above does not meet the specifications, replace the ECM/PCM.
  22.  

  1. Connect a suitable scan tool to read data.
  2.  
  3. Start the engine and run at idle. Warm up the engine to normal operating temperature: 176° to 205°F.
    1. The standard value during idling should be 10 Hz or more.
    2.  
    3. When the engine is revved, the frequency should increase according to the increase in engine speed.
    4.  

  4.  
  5. If the checks above do not meet the specification, disconnect the sensor connector and measure at the harness side.
  6.  
  7. Turn the ignition switch to "ON" position, and measure the voltage between terminal 4 and ground. Voltage should be battery positive voltage.
  8.  
  9. Turn the ignition switch to "LOCK" (OFF) position.
  10.  
  11. If not within specifications, check and repair/replace the connector(s), harness wire between MFI relay and/or the MFI relay.
  12.  
  13. If within specifications, disconnect the sensor connector and measure at the harness side.
  14.  
  15. Turn the ignition switch to "ON" position and measure the voltage between terminal 3 and ground. Voltage should be between 4.8 and 5.2 volts.
  16.  
  17. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 5 and ground. Resistance be less than 2 ohm.
  18.  
  19. If all checks above meet the specifications, replace the sensor.
  20.  
  21. If any check above does not meet the specifications, replace the ECM/PCM.
  22.  

  1. Connect a suitable scan tool to read data.
  2.  
  3. Start the engine and run at idle. Warm up the engine to normal operating temperature: 176° to 205°F.
    1. The standard value during idling should be 10 Hz or more.
    2.  
    3. When the engine is revved, the frequency should increase according to the increase in engine speed.
    4.  

  4.  
  5. If the checks above do not meet the specification, disconnect the sensor connector and measure at the harness side.
  6.  
  7. Turn the ignition switch to "ON" position, and measure the voltage between terminal 4 and ground. Voltage should be battery positive voltage.
  8.  
  9. Turn the ignition switch to "LOCK" (OFF) position.
  10.  
  11. If not within specifications, check and repair/replace the connector(s), harness wire between MFI relay and/or the MFI relay.
  12.  
  13. If within specifications, disconnect the sensor connector and measure at the harness side.
  14.  
  15. Turn the ignition switch to "ON" position and measure the voltage between terminal 3 and ground. Voltage should be between 4.8 and 5.2 volts.
  16.  
  17. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 5 and ground. Resistance be less than 2 ohm.
  18.  
  19. If all checks above meet the specifications, replace the sensor.
  20.  
  21. If any check above does not meet the specifications, replace the ECM/PCM.
  22.  

 
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