Mass Air Flow Sensor (MAF)

OPERATION

The Mass Air Flow (MAF) sensor directly measures the amount of air flowing into the engine. The sensor is mounted between the air cleaner assembly and the air cleaner outlet tube. The sensor utilizes a hot wire sensing element to measure the amount of air entering the engine. The sensor does this by sending a signal, which is generated by the sensor when the incoming air cools the hot wire, to the PCM. The signal is used by the PCM to calculate the injector pulse width, which controls the air/fuel ratio in the engine. The sensor and plastic housing are integral and must be replaced if found to be defective. The sensing element (hot wire) is a thin platinum wire wound on a ceramic bobbin and coated with glass.

This hot wire is maintained at 392°F (200°C) above the ambient temperature as measured by a constant "cold wire''.

A faulty MAF sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit can cause the following symptoms.


Mass Air Flow Sensor Symptoms

  • A no start condition
  • Stalls at idle
  • Surging idle
  • Extended crank time when engine is cold
  • Hesitation
  • Stumble
  • Chuggle
  • Poor fuel economy

Mass Air Flow Sensor Testing

  1. With the engine running at idle, use a DVOM to verify that there are at least 10.5 volts between terminals A and B of the MAF sensor connector. Such a reading indicates that the power input to the sensor is correct. Then, measure the voltage between MAF sensor connector terminals C and D. If the reading is approximately 0.34–1.96 volts, the sensor is functioning properly.

MAF VoltageMAF terminals MAF Harness

Mass Air Flow Sensor Replacement

REMOVAL & INSTALLATION

WARNING
The mass air flow sensor hot wire sensing element and housing are calibrated as a unit and must be serviced as a complete assembly. Do not damage the sensing element, or possible failure of the sensor may occur.

  1. Disconnect the negative battery cable.
  2. Disengage the wiring harness connectors from the IAT and MAF sensors.
  3. Loosen the engine air cleaner outlet tube clamps, then remove the tube from the engine.
  4. Remove the MAF sensor from the air cleaner assembly by disengaging the retaining clips. To remove the MAF sensor, disconnect the PCV system hose from the air cleaner outlet tube . . .

  5. To install:

  6. Install the MAF sensor to the air cleaner assembly and ensure that the retaining clips are fully engaged.
  7. Install the air cleaner outlet tube, then tighten the outlet tube clamps until snug.
  8. Attach the engine wiring harness connectors to the IAT and MAF sensors.
  9. Connect the negative battery cable.
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