Mass Air Flow (MAF) Sensor OPERATION TESTING ,REMOVAL and INSTALLATION?

OPERATION

See Figure 1

The Mass Air Flow (MAF) sensor directly measures the amount of the 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, generated by the sensor when the incoming air cools the hot wire down, 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.

Fig. Fig. 1: The Mass Air Flow (MAF) sensor is mounted to the air cleaner housing

The sensing element (hot wire) is a1 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''.

TESTING

See Figure 2

1. With the engine running at idle, use a DVOM to verify there is at least 10.5 volts between terminals A and B of the MAF sensor connector. This indicates 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.

Fig. Fig. 2: MAF sensor wire harness connections

REMOVAL & INSTALLATION

See Figures 3 through 6

CAUTION

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.

Fig. Fig. 3: To remove the MAF sensor, first disconnect the wire harness plug ...

Fig. Fig. 4: ... then remove the air cleaner-to-throttle body air tube

2. Disengage the wiring harness connector from the MAF sensor, and if necessary, the IAT sensor.
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.

Fig. Fig. 5: Remove the four MAF sensor attaching screws ...

Fig. Fig. 6: ... then remove the sensor from the air cleaner housing

To install:

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

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