The Mass Air Flow (MAF) sensor, found on some engines, measures the amount of air passing through it. The PCM uses this information to determine the operating condition of the engine, to control fuel delivery. A large quantity of air indicates acceleration, while a small quantity indicates deceleration or idle.
The MAF sensor used on these vehicles is of the hot-wire type. Current is supplied to the sensing wire to maintain a calibrated temperature, and as air flow increases or decreases the current will vary. This varying current is directly proportional to air mass.
See Figures 1 and 2
- Visually check the connector, making sure it is connected properly and all of the terminals are straight, tight and free of corrosion.
- With the engine running, lightly tap on the MAF sensor and wiggle the wires at the connector and watch for the idle to change. A common problem is MAF sensor wire damage.
- Backprobe using a DVOM set to the Hertz scale between terminals A and B. Simulate operating conditions by blowing air across the sensor. There should be a frequency swing from the air crossing the wire in the sensor. A normal flow signal will be close to 1200 hertz. If the frequency is not shown, or not proportionate to the air blown across the sensor, the sensor is faulty.
- Check for battery positive (B+) on terminal C and ground on terminal B. If voltage or ground are not present. check the circuits back to the PCM for continuity.
- If you receive the proper amount of voltage at the electrical connector and still have a driveability problem, replace the MAF sensor.
- If the sensor and circuits are functional, the PCM may be faulty.
REMOVAL & INSTALLATION
See Figure 3
- Disconnect the negative battery cable.
- Detach the sensor electrical connection.
- Carefully spread the clamps and remove the air intake ducts from the MAF sensor.
- Remove the sensor from the vehicle.
The arrows on the MAF sensor indicate air flow and MUST point toward the engine.
- Position the MAF sensor into the air ducts and tighten the clamps to 36 inch lbs. (4 Nm) or crimp the clamps, as applicable. If necessary, you can use a very small amount of lubricant on the air duct to help ease installation. Be careful not to get the lubricant in the sensor.
- Attach the sensor electrical connector.
- Connect the negative battery cable.