2010 Toyota Prius FCD Inaccuracy

Discussion in 'Gen 3 Prius Fuel Economy' started by msirach, Jul 28, 2009.

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  1. msirach

    msirach Member

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    I started a new thread for the updates specifically for the issue of the inaccuracy of the FCD (fuel consumption display) on the 2010 Toyota Prius.

    We have about 4500 miles on ours and on every tank the hand calculated MPG is off 3 to 7 MPG from what the FCD reads. My wife gets about 54 MPG on the FCD and her tanks are usually 4 to 5 MPG less calculated. Last week I had two 500 + mile fills and The first was 5.5mpg less and the second 7.1 MPG . This was with a FCD display of 62 MPG which included a lot of around town in Madison for Hybridfest Green Drive Expo. The second tank read 64.4 MPG and it was fully highway driving. It was off by 7.1 MPG .

    5 to 10% is out of the box for error. I fill up at the same station, same pump, same number of clicks, and same direction each time with the exception of the fill in Madison last week of which I estimated slope to be the same at the station I filled at.

    I stopped at the dealer and had them check it out to get a paper trail started. Nothing was found so I followed up with a call to start a claim with customer care the next day. They took my information and later that day, Heather from customer care called back. She gave me a file number to record to use if I called back. She was going to investigate and call me back this week.

    Heather just called back and said she had talked to field service reps and engineers and they informed her they were aware of an accuracy issue of 8% to 10%. They were looking further into the issue and expected something would come out in the form of a TSB.

    Once again I am impressed by the quality of Toyota's attention to their product.
     
    #1 msirach, Jul 28, 2009
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  2. a priori

    a priori Canonus Curiosus

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    I'm just above 5,200 now, and I have very similar results.

    Agreed.

    I'm glad customer service knows about this, is looking into it and is being responsive. Let's hope this gets cleared up sometime soon. If I'm really getting 54MPG+ on a Prius V, I shouldn't be complaining at all. But the fact that the computer tells me I'm really getting 57MPG+ just isn't right (unless the ODO is really messed up).

    Here's a chart showing that my variance really is narrowing in on 5%:

    [​IMG]

    (The above jpeg is a bit degraded. A better view of it is available in the .pdf file listed below.)
     

    Attached Files:

    #2 a priori, Jul 28, 2009
  3. tumbleweed

    tumbleweed Senior Member

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    Have either of you checked the speedometer mileage against a portable GPS? I wonder if it is the distance, the fuel flow, or both that's off? A gas pump could be off by quite a few percent but I doubt all of them are.
     
    #3 tumbleweed, Jul 28, 2009
  4. jay_man2

    jay_man2 jay_man_also

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    There are a couple of other threads on this, and everyone's seeing calculated mpg lower than displayed mpg.

    In previous Toyota's I came to expect that the displayed mpg would be about 1.5 mpg higher than actual, and it was pretty consistent across two RX 330s, a Camry Hybrid, and a Highlander Hybrid.

    Here I'm seeing the display read 1.5 to 3 mpg higher, with the gap getting wider the higher the mpg's. Just today I filled up with the display reading 53.2, and a calculated mpg of 50.2.

    I can't complain about the actual mpg; I'm very happy there. I just wish the displayed mileage was closer to actual.
     
    #4 jay_man2, Jul 28, 2009
  5. ken1784

    ken1784 SuperMID designer

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    Following is copy of my post.
    =====
    Japanese G3 owners are also seeing 5-6% error.
    I saw approx 10% error on the VW Golf. :mad:
    Are there any vehicle which reports the exact same computer MPG as calculated MPG?

    There are a lot of factors to produce computer MPG error, and a car manufacturers doesn't want to display worse computer MPG than calculated(actual) MPG.

    A rumor says that Toyota engineers are going to display intentionally 5% better number on computer MPG for the Gen3 Prius. :mad:

    Ken@Japan
     
    #5 ken1784, Jul 28, 2009
  6. bwilson4web

    bwilson4web BMW i3 and Model 3

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    My testing with a Garmin nuvi showed the indicated MPG was about 1 mph high at 50-70 mph but the trip meter average speed was accurate. Previous tests with my NHW11 showed the speed error is proportional to the milage error from different sized tires.

    Bob Wilson
     
    #6 bwilson4web, Jul 29, 2009
  7. FireEngineer

    FireEngineer Active Member

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    #7 FireEngineer, Jul 29, 2009
  8. MSantos

    MSantos EcoAccelerometry

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    Hi Wayne (and Canadian Gen III owners);

    Like Mike, I also submitted the issue to Toyota Canada Inc. last week notifying them of the issue and the need to have it addressed. I was informed they would look into it ASAP.

    Cheers;

    MSantos
     
    #8 MSantos, Jul 29, 2009
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  9. a priori

    a priori Canonus Curiosus

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    Send the Toyota rep to this thread, Wayne. I'll keep updating the chart I posted above, but it is a slow thing when fill-ups are so far apart!

    I'm thinking the difference is settling in at 5% for me. Ten tanks and 5,000 miles seems like a decent enough sample set.

    BTW: Who did you find that would paint Blue Moon Metallic on your new 2010?
     
    #9 a priori, Jul 29, 2009
  10. EZW1

    EZW1 Active Member

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    The error between calculated and indicated on my '09 seems to follow the same trend. Typically my numbers differ by 4% but I do occasionally get swings as high as 8%. These differences do not track enviornmental conditions like temperature or terrain. So my guess is they're attributable to my driving habit - that is, sometimge I get real aggressive and other times I'm real passive.
     
    #10 EZW1, Jul 29, 2009
  11. basspro

    basspro New Member

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    After four full tanks, I am getting a difference of about 4 to 6 MPG higher showing on the MID vs actual pump measurements.
     
    #11 basspro, Jul 29, 2009
  12. Sho-Bud

    Sho-Bud Member

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    Trust me, most fuel stations aren't honest. I know a few good ones which allways give me a calculated fuel consumption that is equal to the board computer. I know may that each time you fill up, give you a worse calculated average. It's not the Prius's computer.
     
    #12 Sho-Bud, Jul 29, 2009
  13. jay_man2

    jay_man2 jay_man_also

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    Around here the pumps are measured for accuracy by the government on a yearly or semi-yearly basis. It's the computer.
     
    #13 jay_man2, Jul 29, 2009
  14. anne1965

    anne1965 Gotta love the game...

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    Sho-Bud,

    This thread is about the Gen III.

    You drive a Gen II Prius. That didn't have a FCD problem. I think it underestimated by 0.1 l/100 or 2-3%.

    I'm only on my second Gen III tank and I don't know how full the first tank was delivered by the garage. Real consumption vs computed was 3.9 and 4.27 l/100 km resp. After emptying my 2nd tank I can say more.
     
    #14 anne1965, Jul 29, 2009
  15. ken1784

    ken1784 SuperMID designer

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    Our observation is 2% accuracy on the Gen2 and 5% on the Gen3.

    Ken@Japan
     
    #15 ken1784, Jul 29, 2009
  16. cossie1600

    cossie1600 Active Member

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    The rental 08 I had was always off 5mpg. After one tank, my 2010 seems to be within 1mpg. But then seriously, does it really make that much of a difference.
     
    #16 cossie1600, Jul 29, 2009
  17. msirach

    msirach Member

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    I just filled ours again. My wife drove this tank and here are the results:
    4950 miles
    487 miles @ 54.4 fcd
    48.68 MPG calculated for a difference of 5.72 MPG or 10.625%
     
    #17 msirach, Jul 30, 2009
  18. a priori

    a priori Canonus Curiosus

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    What is the lifetime difference now?

    My most recent fill-up was at 4,999 miles
    503.8 miles @ 61.3 (on the MID)
    58.4 MPG calculated for a difference of 2.9 MPG or 5.0%
    Lifetime at 4,999: 57.0 on MID and 54.3 calculated for a difference of 2.7 MPG or 5.0%
     
    #18 a priori, Jul 30, 2009
  19. msirach

    msirach Member

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    Prior tanks are on a pc at home. I am away for a few days and will post the tally when I return.
     
    #19 msirach, Jul 30, 2009
  20. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    glad its not only me...check my sig...last tank difference was 8 MPG...

    several times. using 2 different GPS systems, no real differences. over 30 miles one system was .2 miles off, the other dead on.
     
    #20 DaveinOlyWA, Aug 1, 2009
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