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MAF Sensor, What is it, Where is it

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by WMIToni, Feb 3, 2010.

  1. WMIToni

    WMIToni New Member

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    Just catching up on my reading, I came upon a reference to an MAF sensor and the owner's ability to change it. So what is it, and where is it? I ask because I'm on my fourth sensor replacement in an 05 and the dealer is not cheap.
     
    #1 WMIToni, Feb 3, 2010
  2. efusco

    efusco Moderator Emeritus
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    #2 efusco, Feb 3, 2010
  3. efusco

    efusco Moderator Emeritus
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    5 Sensor replacements?? That doesn't sound right. At most it should be a 'clean' item with the rare burn out and replacement.
     
    #3 efusco, Feb 3, 2010
  4. WMIToni

    WMIToni New Member

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    The oxygen sensor has been replaced twice, the headlight sensor once, and I'd have to look up the fourth. The service dept just smiles and shrugs. Thanks for the info though on the last one. Maybe I can prevent a return to the dealership. I looked at the illustrations, but still not sure of what the sensor is supposed to do or when I'll know if it has a problem. That is assuming I don't try to clean it first.
     
    #4 WMIToni, Feb 3, 2010
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Where is it: mounted to the throttle body, see the illustrations in the link provided by Evan. This is immediately visible when you open the hood and look at the throttle body.

    What does it do: the mass air flow sensor helps the engine ECU to monitor the flow of air through the throttle body. The engine ECU heats a platinum wire in the sensor to a specific temperature, then keeps track of the electric current required to maintain that temp. As more current is needed, the ECU assumes that a greater flow of air is passing by this wire, thus cooling it down faster.

    Why does it do this: to help the engine ECU maintain the correct air/fuel mixture. If the ECU knows how much air is entering the engine, it will know how much fuel to inject. The air/fuel ratio sensor upstream of the catalytic converter also provides data to the ECU to help determine the appropriate air/fuel mixture. The benefit of the MAF sensor design is that it automatically adjusts air/fuel mixture as you drive the car in higher altitudes where the air is less dense.

    How to know if it has a problem: in severe cases the engine will not start and/or a DTC code may be logged. In a marginal case you may find your mpg is decreasing for no apparent reason.

    How to clean: buy a can of MAF sensor cleaning fluid, remove the MAF sensor, and follow directions on the can. Do not use alternate cleaning products.

    How to avoid/reduce the need to clean: change your engine air filter regularly. I do this at 15K mile intervals.
     
    #5 Patrick Wong, Feb 3, 2010
    TsKarma likes this.
  6. WMIToni

    WMIToni New Member

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    Thank you I now know what to be aware of and what to do about it. I really am tired of paying out big bucks to the dealership for sensors.

     
    #6 WMIToni, Feb 4, 2010
  7. Bob64

    Bob64 Sapphire of the Blue Sky

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    What caused you to have the dealer change it?

    Did you get a warning light? check engine light?
     
    #7 Bob64, Feb 4, 2010
  8. srivenkat

    srivenkat Active Member

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    Patrick: do you replace the air filter even if it's not dirty?
     
    #8 srivenkat, Apr 30, 2013
  9. Bronze84

    Bronze84 Member

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    FYI :)

    Dirty...

    [​IMG]

    [​IMG]

    Clean...

    [​IMG]

    [​IMG]
     
    #9 Bronze84, Apr 30, 2013
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    15K mile intervals was appropriate when I lived in southern CA. Now that I live in an area with cleaner air, I inspect the air filter and will replace only when it has sufficient dirt collected in the filter element so that light does not pass through the filter.
     
    #10 Patrick Wong, Apr 30, 2013
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