Ford Full-Size Vans 1989-1996 Repair Guide

Mass Air Flow (MAF) Sensor



The Mass Air Flow (MAF) sensor directly measures the mass of the air flowing into the engine. The sensor output is an analog signal ranging from about 0.5-5.0 volts. The signal is used by the PCM to calculate the injector pulse width. The sensing element is a thin platinum wire wound on a ceramic bobbin and coated with glass. This "hot wire" is maintained at 200°C above the ambient temperature as measured by a constant "cold wire". The MAF sensor is located in the outlet side of the air cleaner lid assembly.


OBD-I System
  1. Make sure the ignition key is OFF .
  3. Connect Breakout Box T83L-50-EEC-IV or equivalent, to the PCM harness and connect the PCM.
  5. Start the engine and let it idle.
  7. Use a voltmeter to measure the voltage between test pin 50 of the Breakout Box and the battery negative post.
  9. Replace the MAF sensor if the voltage is not 0.36-1.50 volts.

OBD-II System

See Figure 1

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Fig. Fig. 1: MAF sensor wiring schematic-OBD-II system shown, others similar

  1. Using a multimeter, check for voltage by backprobing the MAF sensor connector.
  3. With the engine running at idle, verify there is at least 10.5 volts between the VPWR and PWR GND terminals of the MAF sensor connector. If voltage is not within specification, check power and ground circuits and repair as necessary.
  5. Check voltage between the MAF and MAF RTN terminals. Voltage should be approximately 0.34-1.96 volts. If voltage is not within specification, the sensor may be faulty.


See Figure 2

Click image to see an enlarged view