Mazda Trucks 1994-1998 Repair Guide

Mass Air Flow (MAF) Sensor

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OPERATION



See Figure 1

The Mass Air Flow (MAF) sensor directly measures the amount of the air flowing into the engine. The sensor is mounted between the air cleaner assembly and the air cleaner outlet tube.

The sensor utilizes a hot wire sensing element to measure the amount of air entering the engine. The sensor does this by sending a signal, generated by the sensor when the incoming air cools the hot wire down, to the PCM. The signal is used by the PCM to calculate the injector pulse width, which controls the air/fuel ratio in the engine. The sensor and plastic housing are integral and must be replaced if found to be defective.



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Fig. Fig. 1: The Mass Air Flow (MAF) sensor is mounted to the air cleaner housing

The sensing element (hot wire) is a thin platinum wire wound on a ceramic bobbin and coated with glass. This hot wire is maintained at 392°F (200°C) above the ambient temperature as measured by a constant "cold wire".

TESTING



Navajo and B Series Pick-up Models

See Figure 2

  1. With the engine running at idle, use a DVOM to verify there is at least 10.5 volts between terminals A and B of the MAF sensor connector. This indicates the power input to the sensor is correct. Then, measure the voltage between MAF sensor connector terminals C and D . If the reading is approximately 0.34-1.96 volts, the sensor is functioning properly.
  2.  



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Fig. Fig. 2: MAF sensor wire harness connections

MPV Models
1994-95-2.6L ENGINE

See Figures 3, 4 and 5

  1. Remove the rubber boot from the Mass Air Flow (MAF) sensor wiring connector.
  2.  
  3. Using a voltmeter, measure the terminal voltages. Refer to the specifications chart.
  4.  



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Fig. Fig. 3: Using a voltmeter to measure terminal voltages



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Fig. Fig. 4: MAF sensor voltage specifications chart



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Fig. Fig. 5: MAF sensor schematic

  1. If not as specified, inspect the wiring harness for an open or short circuit. If the wiring is okay, check the burn off operation as follows:
    1. Disconnect the negative battery cable for 20 seconds and reconnect it.
    2.  
    3. Start the engine and allow it to warm up to operating temperature.
    4.  
    5. Remove the rubber boot from the Mass Air Flow (MAF) sensor wiring connector.
    6.  
    7. Run the engine for more than 5 seconds at approximately 2000 rpm in neutral.
    8.  
    9. Turn the ignition switch OFF and check the voltage at the MAF sensor terminal wire (G/O) and terminal 2H of the powertrain control module. There should be 0 volts just after the ignition switch is turned OFF, then approximately 8 volts battery positive voltage momentarily 2-5 seconds after turning the ignition switch OFF.
    10.  

  2.  
  3. If not as specified, replace the MAF sensor.
  4.  

1996-98-3.0L ENGINE

See Figure 6

  1. Inspect the MAF sensor for damage and cracks.
  2.  
  3. Start the engine and allow it to warm up to operating temperature.
  4.  
  5. Shift the gear selector lever to the P (PARK) position.
  6.  
  7. Make sure that all electrical loads are turned OFF. (Ex. headlights, blower motor, etc.)
  8.  
  9. Connect the New Generation Star (NGS) tester, or equivalent scan tool, to the data link connector, located under the driver side dashboard.
  10.  
  11. Select the "PID/DATA MONITOR AND RECORD" function of the tester display.
  12.  
  13. Select "MAF V" on the tester display. The voltage should read as follows:

    Ignition switch ON: 0.5-1.0 Volts
     
    Engine at idle: 1.0-2.0 Volts
     

  14.  



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Fig. Fig. 6: Mas air flow sensor connector terminal identifications

  1. If not as specified, inspect the following:

    Harness continuity between PCM terminal 3B and MAF sensor connector terminal B
     
    Harness continuity between PCM terminal 4A and MAF sensor connector terminal E
     
    Harness continuity between main relay terminal D and MAF sensor connector terminal A
     
    Turn the ignition switch to the ON position and measure for battery positive voltage at MAF sensor connector terminal A.
     

  2.  
  3. Measure the resistance between MAF sensor connector terminals C and D. The resistance should measure 2.21-2.69k ohms at 68°F (20°C).
  4.  
  5. If there is incorrect terminal voltage, harness continuity or resistance measurements, replace the MAF sensor.
  6.  

REMOVAL & INSTALLATION



See Figures 7, 8, 9 and 10


CAUTION
The mass air flow sensor hot wire sensing element and housing are calibrated as a unit and must be serviced as a complete assembly. Do not damage the sensing element or possible failure of the sensor may occur.

  1. Disconnect the negative battery cable.
  2.  



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Fig. Fig. 7: To remove the MAF sensor, first disconnect the wire harness plug ...



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Fig. Fig. 8: ... then remove the air cleaner-to-throttle body air tube

  1. Disengage the wiring harness connector from the MAF sensor, and if necessary, the IAT sensor.
  2.  
  3. Loosen the engine air cleaner outlet tube clamps, then remove the tube from the engine.
  4.  
  5. Remove the MAF sensor from the air cleaner assembly by disengaging the retaining clips.
  6.  



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Fig. Fig. 9: Remove the four MAF sensor attaching screws ...



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Fig. Fig. 10: ... then remove the sensor from the air cleaner housing

To install:

If necessary, be sure to align the arrow on the MAF sensor with the direction of the air flow.

  1. Install the MAF sensor to the air cleaner assembly and ensure that the retaining clips are fully engaged.
  2.  
  3. Install the air cleaner outlet tube, then tighten the outlet tube clamps until snug.
  4.  
  5. Attach the engine wiring harness connectors to the IAT and MAF sensors.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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