See Figure 1
The Mass Air Flow (MAF) sensor directly measures the mass of air being drawn into the engine. The sensor output is used to calculate injector pulse width. The MAF sensor is what is referred to as a "hot-wire sensor". The sensor uses a thin platinum wire filament, wound on a ceramic bobbin and coated with glass, that is heated to 200°C (417°F) above the ambient air temperature and subjected to the intake airflow stream. A "cold-wire" is used inside the MAF sensor to determine the ambient air temperature.
Battery voltage from the EEC power relay, and a reference signal and a ground signal from the PCM are supplied to the MAF sensor. The sensor returns a signal proportionate to the current flow required to keep the "hot-wire" at the required temperature. The increased airflow across the "hot-wire" acts as a cooling fan, lowering the resistance and requiring more current to maintain the temperature of the wire. The increased current is measured by the voltage in the circuit, as current increases, voltage increases. As the airflow increases the signal return voltage of a normally operating MAF sensor will increase.
See Figures 2, 3 and 4
- Using a multimeter, check for voltage by backprobing the MAF sensor connector.
- With the key ON , and the engine OFF , verify that there is at least 10.5 volts between the VPWR and GND terminals of the MAF sensor connector. If voltage is not within specification, check power and ground circuits and repair as necessary.
- With the key ON , and the engine ON , verify that there is at least 4.5 volts between the SIG and GND terminals of the MAF sensor connector. If voltage is not within specification, check power and ground circuits and repair as necessary.
- With the key ON , and the engine ON , check voltage between GND and SIG RTN terminals. Voltage should be approximately 0.34-1.96 volts. If voltage is not within specification, the sensor may be faulty.
REMOVAL & INSTALLATION
See Figures 5 through 9
- Disconnect the negative battery cable.
- Unplug the MAF and IAT sensors connectors.
- Release the retaining clips from the air cleaner cover.
- Remove the air cleaner outlet tube from the throttle body(2.5L) or resonator (2.0L)and remove the outlet tube and air cleaner cover assembly.
- Loosen the hose clamps and remove the outlet tube from the MAF sensor.
- Remove the MAF retaining clips (2.0L) or bolts (2.5L) from the air cleaner cover.
- Carefully remove the MAF from the cover.
On the 2.5L engine:
- Replace the gasket between the MAF and the air cleaner cover.
- Install the MAF onto the air cleaner cover and tighten the retaining bolts to 25 inch lbs. (3.5 Nm).
On the 2.0L engine:
- Inspect the O-ring on the MAF and replace if necessary.
- Install the MAF onto the air cleaner cover and attach the retaining clips.
- Install the outlet tube onto the MAF and tighten the hose clamps.
- Install air cleaner outlet tube and cover into place and attach the retaining clips for the cover and tighten the hose clamps on the throttle body(2.5L) or resonator (2.0L).
- Attach the connectors on the IAT and the MAF sensors.
- Connect the negative battery cable.