Yaris 2007

Mass Air Flow Meter

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Location



Specific to:

Toyota Yaris 2007-2010

Refer to the accompanying illustration.

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Fig. Locating the MAF meter

Operation



Specific to:

Toyota Yaris 2007-2010

The Mass Air Flow (MAF) meter is a Positive Coefficient Thermistor (PTC) that determines the volume of air flowing into the intake system. The MAF meter operates within a 5 volt DC reference range, and provides a linear input signal to the Powertrain Control Module (PCM) that is based upon the measured engine intake air temperature. The thermistor, or -hot wire- is heated to a pre-determined temperature, and the then cools as the volume of air flowing past the wire increases. The PCM uses data from the MAF meter to calculate air-fuel mixture, ignition timing, and fuel injector pulse width. The MAF meter is sometimes integrated with the Intake Air Temperature (IAT) Sensor as a physical component.

Removal & Installation



Specific to:

Toyota Yaris 2007-2010

  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the wire harness clamp and Mass Air Flow (MAF) meter connector.
  4.  
  5. Remove the 2 screws and the Mass Air Flow (MAF) meter.
  6.  
  7. Remove the O-ring from the Mass Air Flow (MAF) meter.
  8.  
  9. To install, reverse the removal procedure.
  10.  
  11. Install a new O-ring on to the MAF sensor.

    Click image to see an enlarged view

    Fig. Locating the MAF sensor

  12.  

Testing



Specific to:

Toyota Yaris 2007-2010


NOTE
Refer to the Electrical Wiring Diagram for component and connector locations, connector views, and circuit-specific information.

MAF Circuit Testing

Specific to:

Toyota Yaris 2007-2010

Use a suitable scan tool, a Graphing Multi-Meter (GMM), or a Digital Volt-Ohm Meter (DVOM) in order to view the MAF data.

MAF Sensor logic is relative to the scale of resistance: when the intake air volume is low, the voltage is decreased. When the coolant temperature is high, the voltage is increased.

Inspect the air intake tube, the engine air filter, and the MAF and/or IAT sensors for contamination and physical damage in order to verify that the air induction system is in proper working order. If an air induction system fault is evident, repair as required before continuing.

If a DVOM is being used, additional information may be acquired by taking measurements at the sensor connector as well as the PCM connector. If a significant voltage drop is measured (greater than 0.5 volts DC), check the wiring harness and connections for corrosion, poor pin connections, or damaged wires.

If all engine wiring and pin connections are confirmed, disconnect the MAF Sensor to verify the signal with a DVOM, and verify PCM communication before replacing the MAF Sensor.

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Fig. MAF Sensor Range Chart

MAF Sensor Strategy

Specific to:

Toyota Yaris 2007-2010

The MAF Sensor provides a linear input signal to the Powertrain Control Module (PCM) for a number of engine control system calculations. The MAF signal is compared with Manifold Absolute Pressure (MAP), Intake Air Temperature (IAT), Engine Coolant Temperature (ECT), and Fuel Trim (HO2S) in order to determine the correct air-fuel mixture for measured operating conditions.

Related Diagnostic Trouble Codes

Specific to:

Toyota Yaris 2007-2010



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Fig. Related Diagnostic Trouble Codes

 
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