GM Astro/Safari 1985-1996 Repair Guide

Mass Air Flow (MAF) Sensor

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OPERATION



See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: The mass air flow sensor directly measures the amount of air entering the engine

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.

TESTING



  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.  

REMOVAL & INSTALLATION



See Figures 2 and 3



Click image to see an enlarged view

Fig. Fig. 2: This style MAF sensor is mounted directly behind the air cleaner assembly



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Fig. Fig. 3: Dirty contacts can cause the MAF to send bad signals to the ECM, so check it before installation

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the electrical connector.
  4.  
  5. Remove the air intake hoses from the sensor, then remove its attaching bolts, if equipped on some versions.
  6.  
  7. Installation is the reverse of removal.
  8.  

 
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