Mazda Trucks 1987-1993 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

TESTING



Navajo

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

Pick-up and MPV Models
MAF SENSOR

See Figures 3 and 4

  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

  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.  

VOLUME AIR FLOW SENSOR

See Figures 5 through 10

Testing of the volume air flow sensor also includes testing of the integral intake air temperature sensor.



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Fig. Fig. 5: Checking the resistance of the volume airflow sensor with the shutter closed



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Fig. Fig. 6: Checking the resistance of the volume airflow sensor while moving the shutter



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Fig. Fig. 7: Using a voltmeter with a temperature probe (A), an ohmmeter (B) and a hairdryer (C), measure the resistance fluctuation of the integral intake air temperature sensor



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Fig. Fig. 8: Checking the resistance of the intake air temp sensor

  1. Remove the volume air flow sensor from the vehicle.
  2.  
  3. Inspect the volume air flow sensor for cracks or any other signs of damage.
  4.  
  5. Check that the sensor shutter plate opens and closes smoothly.
  6.  



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Fig. Fig. 9: Volume air flow sensor terminal identifications



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Fig. Fig. 10: Resistance specifications for the volume air flow sensor

  1. Using an ohmmeter, open and close the sensor shutter plate while checking the resistance between the terminals.
  2.  
  3. Using a voltmeter with a temperature probe, an ohmmeter and a hairdryer for temperature variation, measure the resistance fluctuation of the integral intake air temperature sensor.
  4.  
  5. If the resistance does not measure within specifications, replace the volume air flow sensor.
  6.  

REMOVAL & INSTALLATION



See Figures 11, 12, 13 and 14


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



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Fig. Fig. 12: ... 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. 13: Remove the four MAF sensor attaching screws ...



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Fig. Fig. 14: ... 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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