GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Mass Air Flow (MAF) Sensor



The Mass Air Flow sensor, used on 3.0L (VIN L) and 3.3L (VIN N) engines, replaces the MAP sensor used on other engines. The MAF sensor is located in the incoming air stream and measures the amount of air that passes through the electrical grid. The MAF indicates air flow to the computer control module as an electrical value. The ECM uses this information to determine the operating condition of the engine in order to determine fuel requirements. A large quantity of air passing through the MAF will be read by the computer control module as acceleration condition and a small quantity as deceleration or idle.


See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Terminals C and B supply voltage to the MAF sensor

  1. Visually check the connector, making sure it is properly connected, and the terminals are straight, tight, and free of corrosion.
  3. With the engine running, lightly tap on the MAF sensor and wiggle the wires at the connector; if the idle speed fluctuates, it is possible that the connector is damaged.
  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 Hz. If the freqency is not shown, or not proportionate to the air blown across the sensor, the sensor is faulty.
  7. Check for battery positive (B+) on terminal C and ground on terminal B. If voltage or ground is not present, check the circuits back to the PCM for continuity.
  9. If you still receive a proper amount of voltage at the electrical connector and still have a driveability problem, it is probable that the MAF sensor will need to be replaced.
  11. If the sensor and circuits are functional, the PCM may be faulty.


See Figures 2 and 3

  1. Disconnect the negative battery cable.
  3. Unfasten the air cleaner-to-throttle body retaining screw.
  5. Unsnap the clips on the air cleaner assembly, then remove the air cleaner housing from the throttle body.

Click image to see an enlarged view

Fig. Fig. 2: View of the Mass Air Flow (MAF) sensor mounting-3.0L engine

  1. Detach the electrical connector.
  3. Unfasten the retaining screws, then remove the MAF sensor from the engine.

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Fig. Fig. 3: View of the Mass Air Flow (MAF) sensor-3.3L engine

  1. Installation is the reverse of the removal procedure.