GM Full Size Vans 1987-1997 Repair Guide

Mass Air Flow (MAF) Sensor

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OPERATION



See Figure 1

The Mass Air Flow (MAF) Sensor measures the amount of air entering the engine during a given time. The ECM uses the mass airflow information for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle.



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Fig. Fig. 1: Exploded view of the Mass Air Flow (MAF) sensor

TESTING



See Figure 2

  1. Backprobe with a high impedance voltmeter between MAF sensor terminals C and B.
  2.  
  3. With the ignition ON engine off, verify that battery voltage is present.
  4.  
  5. If the voltage is not as specified, either the wiring to the MAF sensor, fuse or the ECM may be faulty. Correct any wiring or ECM faults before continuing test.
  6.  
  7. Disconnect the voltmeter and backprobe with a frequency meter between MAF sensor terminals A and B.
  8.  
  9. Start the engine and wait until it reaches normal idle speed and verify that the MAF sensor output is approximately 2000 Hz.
  10.  
  11. Slowly raise engine speed up to maximum recommended rpm and verify that the MAF sensor output rises smoothly to approximately 8000 Hz.
  12.  
  13. If MAF sensor output is not as specified the sensor may be faulty.
  14.  



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Fig. Fig. 2: Mass Airflow (MAF) sensor wiring diagram

REMOVAL & INSTALLATION



See Figures 3, 4 and 5

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the electrical connector.
  4.  
  5. Remove the air intake duct and the sensor.
  6.  
  7. Installation is the reverse of removal.
  8.  



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Fig. Fig. 3: Unplug the MAF sensor electrical connection ...



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Fig. Fig. 4: ... then loosen the intake duct retainers



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Fig. Fig. 5: Remove the intake duct and MAF sensor from the engine compartment

 
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