GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Mass Air Flow (MAF) Sensor Repair Guide



See Figure 1

The Mass Air Flow (MAF) Sensor measures the amount of air entering the engine during a given time. The VCM 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: View of the Mass Air Flow (MAF) sensor


See Figure 2

  1. Backprobe with a high impedance voltmeter between MAF sensor terminals C and B .
  3. With the ignition ON engine off, verify that battery voltage is present.
  5. If the voltage is not as specified, either the wiring to the MAF sensor, the fuse, or the VCM may be faulty. Correct any wiring or VCM faults before continuing test.
  7. Disconnect the voltmeter and backprobe with a frequency meter between MAF sensor terminals A and B .
  9. Start the engine and wait until it reaches normal idle speed and verify that the MAF sensor output is approximately 99 Hz.
  11. Slowly raise engine speed up to maximum recommended rpm and verify that the MAF sensor output rises smoothly to approximately 8000 Hz.
  13. If MAF sensor output is not as specified the sensor may be faulty.

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Fig. Fig. 2: Typical Mass Airflow (MAF) sensor wiring diagram (wire color, terminal identification/location may vary on certain models)


  1. Disconnect the negative battery cable.
  3. Unplug the electrical connector.
  5. Remove the air intake hoses from the sensor, then remove the sensor.
  7. Installation is the reverse of removal.
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