GM Corsica/Beretta 1988-1996 Repair Guide

Mass Air Flow (MAF) Sensor

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OPERATION



The Mass Air Flow (MAF) sensor, found on the 1996 3.1L engine, measures the amount of air passing through it. The PCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration, while a small quantity indicates deceleration or idle.

The MAF sensor used on these vehicles is of the hot-wire type. Current is supplied to the sensing wire to maintain a calibrated temperature, and as air flow increases or decreases the current will vary. This varying current is directly proportional to air mass.

The MAF sensor on the 3.8L engine is attached to the throttle body. On the 5.7L engine, the MAF sensor is mounted between the air ducts.

TESTING



See Figure 1

  1. Visually check the connector, making sure it is connected properly and all of the terminals are straight, tight and free of corrosion.
  2.  
  3. With the engine running, lightly tap on the MAF sensor and wiggle the wires at the connector and watch for the idle to change. A common problem is MAF sensor wire damage.
  4.  
  5. Backprobe using a DVOM set to the Hertz scale between terminals A and B. Simulate operating conditions by blowing air across the sensor. There should be a frequency swing from the air crossing the wire in the sensor. A normal flow signal will be close to 1200 hertz. If the frequency is not shown, or not proportionate to the air blown across the sensor, the sensor is faulty.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: Mass Air Flow (MAF) sensor circuit

  1. Check for battery positive (B+) on terminal C and ground on terminal B. If voltage or ground are not present. check the circuits back to the PCM for continuity.
  2.  
  3. If you receive the proper amount of voltage at the electrical connector and still have a driveability problem, replace the MAF sensor.
  4.  
  5. If the sensor and circuits are functional, the PCM may be faulty.
  6.  

REMOVAL & INSTALLATION



See Figures 2, 3 and 4

  1. Disconnect the negative battery cable.
  2.  
  3. Carefully the clamps and remove the air intake ducts from the MAF sensor.
  4.  
  5. Detach the sensor electrical connection.
  6.  



Click image to see an enlarged view

Fig. Fig. 2: Unplug the Mass Air Flow (MAF) sensor electrical connector ...



Click image to see an enlarged view

Fig. Fig. 3: ... then remove the MAF sensor from the vehicle



Click image to see an enlarged view

Fig. Fig. 4: The MAF sensor, found on the 1996 3.1L engine, is mounted between the air intake ducts

  1. Remove the MAF sensor from the air filter housing.
  2.  

To install:

The arrows on the MAF sensor indicate air flow and MUST point toward the engine.

  1. Position the MAF sensor into the air ducts and tighten the clamps to 36 inch lbs. (4 Nm).
  2.  
  3. Attach the sensor electrical connector.
  4.  
  5. Connect the negative battery cable.
  6.  

 
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