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Attention Prius Owners, I believe I have discovered a previously unknown Mechanism of Low MPG.

Discussion in 'Gen 2 Prius Main Forum' started by TheLastMojojomo, Nov 2, 2021.

  1. ChapmanF

    ChapmanF Senior Member

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    There really isn't anything Toyota calls a "standard ECU relearn". There are a number of different procedures, some of which involve jumpers between CG and Tc or Ts and various amounts of time or other little dance steps, and it's a mark of wisdom to first know what any specific dance one is thinking of doing is really there for, before deciding when or whether to do it. The deets are in the repair manual, but of course there's not one place in it where they all are; each subsystem has its own section.

    Toyota Service Information and Where To Find It | PriusChat
     
  2. Gen2khar

    Gen2khar New Member

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    I noticed I get 60+ mpg city driving no more than 45mph by first driving the car for 20mins when the engine is warmed up I disconnect the 12v battery for a few mins and then when I drive it shows around 60mpg even in winter and I tried this a few times to confirm. Just tried uploading a pics of my mfd but it shows a error?? I’m new this is my first time using this site so sorry.

    Anyone be kind enough to measure the rubber headlight bulb dust cap size please. Thanks I got flies in my headlight and the prices are to much so will just by universal ones but not sure if it’s 8” or 9”
     
  3. ChaseE

    ChaseE Junior Member

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    So I have the 2003-2006 Toyota Factory Repair Manual now...where are the ECU reset procedures, because I can't find them anywhere?
     
  4. ChapmanF

    ChapmanF Senior Member

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    Is there such a thing? I didn't think they bundled up years like that. What's the publication number?

    As far as I know, when you go to TIS, you find your specific repair manual by model and year.

    Toyota Service Information and Where To Find It | PriusChat

    In what I've seen of those, each major subsystem (engine, hybrid system, brakes, steering, you name it) is its own major section, and procedures involving each ECU in the car are found in the section where that ECU belongs.
     
  5. AdamD

    AdamD Junior Member

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    I have a gen2 prius, 2004 with 225k original traction battery.
    Using torque... full or depleted, the traction battery cell pairs are all within 0.1v of each other..... I'm truly amazed. (used torque and setup 14 gauges showing min/max voltages of the 14 pairs (28 batteries).

    I graphed pedal angle, ICE rpm, and battery SOC

    When my battery SOC is near max, at 28-32deg pedal angle, the engine turns on. I repeated this multiple times on flat, slight incline, slight decline.
    The 30deg pedal angle has been that way during my ownership (30k-225k).

    Currently I drive 30miles freeway, 55-75mph every morning... coming home varies, but typically 40-65mph.

    So based on what I can read, I'm in "weak ev" mode...

    Side note:
    Oh yeah.. I recently decided to check my 12V battery in the morning (car in garage).. uh oh. 11.0v
    I turn on the headlights... 10.9... 10.8.... 10.7....10.6...10.5...(less than 2 minutes total).. I stopped there.
    Put it on smart charger for a day.. checked voltage. 11.4. heh.
    Optima yellowtop... it'll be 9 years old in May. I'm ok with that. Have a new battery coming next week.
     
    #105 AdamD, Jan 21, 2024
    Last edited: Jan 21, 2024
  6. qmanqman

    qmanqman Active Member

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    Not trying to be a smartass but was this thread useful to anyone? I didn't read it all just a sample of a few posts.

    I just thought that even if this is true, so what? If you need to disconnect your 12V battery what are you gonna do?
     
  7. AdamD

    AdamD Junior Member

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    You can put a memory maintainer... you can get one that plugs into your ODB2 port, 12v port, or just connect a battery to your 12v jump point under the hood. That way when you unplug your 12v battery, you wont lose memory/settings
     
  8. Darklandscape

    Darklandscape Junior Member

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    When I changed my 12 volt to a new one and ran my city mpg test I got a 7-8 mpg increase.
    My old 12 volt was at 50k miles. Would be great if you can test this on your prius, mine is gone.
     
  9. Chimi1

    Chimi1 Junior Member

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    30v diff in two readings would likely point to trac batt temp starting and running, high temp texas here so when I leave work 5-6pm on a summer day the trak pak is 114-120 with the windows cracked and windshield sunblocker, most recently a 20'' strip of ceramic 80%(temu) tint on the front windshield, (30% front 25% rears) always, on those summer days just starting to hit the road, dr.prius app was all reds just discharge mode for the first 15-20 min of driving, ice kicking in at 3mph, anywho started just using the fan bypass on the dr.prius app as well as the as seen on tv "auto cool" lol totally needed as the ac is aged and a bit weak for tx heat everything helps !!! plus i sweat quickly and have a shaved head so no bueno, but yes take note of the temp diff of the two readings as well as the resistance
     
  10. Chimi1

    Chimi1 Junior Member

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    das what i been saying lol, once i changed my black bus bars that were pitted as well ev throttle improved greatly as well as resistance in the pack dropped !
     
  11. TheLastMojojomo

    TheLastMojojomo Active Member

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    I know I've been MIA on this thread for awhile... but I'm still working on this. I'll be picking up on working on this during the Spring. During the winter I don't drive my Prius much and get busy with work.

    The reason you see one attached photo having a resistance reading of 19 mOhms even at 58% SOC is because the default of the Battery ECU is 19Mohms... the Battery ECU uses a sliding average to calculate resistance between 77-116°F... outside of this range the battery ecu does not display resistance as a viewable OBDII parameter. My guess is the Battery ECU in the 2nd attached photo had recently been reset causing 19 mOhms across the board as well as potentially a different State of Charge % reading.

    The post your replying to was very early in the thread working on this low mpg mechanism... I have a much more solidified understanding of what's happening now and specifically how temperature can effect EV Mode behavior.

    I'll post again below the preliminary YouTube video I made describing the Low mpg mechanism and how it effects EV Mode:



    The final video will be much more comprehensive and describe how EV Mode is effected much clearer. I threw the above video together relatively quickly to lay groundwork that this WEAK EV State Low mpg mechanism could be widespread.
     
  12. TheLastMojojomo

    TheLastMojojomo Active Member

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    A very small update to this thread:


    I am beginning to work on the final write-up for this low mpg mechanism again. I made the short video above. The EV Mode button video on the left is simulating the MAX EV State and how my Prius behaved before a 12v Disconnect in early 2020. The Video on the right shows the WEAK EV State and how my Prius has behaved for the past 4 years. The videos above were taken on the same mail route one day after the other after delivering a package to the same church parking lot so terrain and acceleration metrics are nearly identical... but I did accelerate slightly faster in the video on the right. I changed the audio pitch and lowered the volume in the right video so the sounds of each can be distinguished better. You can see how much greater the EV Output is in the left video compared to the right even on a lower State of Charge. This shows how City Mpg can be effected by 5-10+ given the right circumstances when in the WEAK EV State compared to the MAX EV State.

    Also, I believe I have discovered this issue is also present in the Gen 4 Prius/Toyota Hybrid Platform. I messaged with a Redditor recently who seems to be describing the WEAK EV State after a Software update:

     
    #112 TheLastMojojomo, Apr 1, 2024
    Last edited: Apr 1, 2024
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  13. TheLastMojojomo

    TheLastMojojomo Active Member

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    I have made another short Graphic Video to describe the EV States:



    5x Speed Version:


    This video is probably the most condensed yet informative piece of information I've made yet. If you watch it several times, the average Prius owner should start to understand the WEAK EV State low mpg mechanism I am trying to describe.

    Doing the same as the last post... this is a Business Park section of my mail route synced one day after the other. The right is me driving normally in the
    WEAK EV State... the left is me driving in the WEAK EV State but using the EV Mode button as frequently as possible to mimick the MAX EV State. You will see how the Prius uses significantly more EV Output to propel the vehicle on the left side compared to the right. For this portion of the mail route, the EV Mode button equates directly to how my Prius behaved years ago when in the MAX EV State. I will have another video uploaded shortly with dozens of different mail route sections synced just like this one.

    I recommend watching in 4k if possible as it makes it easier to read the text. The video is purely graphical in nature and there is a lot to read and understand on screen... but if you watch it several times taking more information each time, the difference between the MAX and WEAK EV States should become clear. If you're trying to compare the two video graphics at the bottom while they're playing... keep whatever device your using to watch a decent distance away from your face as it's easier to process that way.
     
    #113 TheLastMojojomo, Apr 3, 2024
    Last edited: Apr 3, 2024
  14. TheLastMojojomo

    TheLastMojojomo Active Member

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    A fairly significant update -
    I am now all but certain the WEAK EV State has the potential to effect every single Toyota Hybrid on the road. I have found a post on the Rav4 Hybrid Subreddit that describes the WEAK EV State Hyperaccurately after hours of scouring. It's a 5th generation 2020 Rav4 that the poster owns... the most recent model/generation:

    [​IMG]
    The description of this post is excedingly similar to how @davyk described the WEAK EV State almost 2 decades ago for their Gen 2 Prius:

    [​IMG]

    The only reason this issue has remained in the dark for so long is that 99.9% of Prius owners do not describe it accurately and it is otherwise completely phantom unless you know how to describe the behavior. If exposed this truly could lead to a 100+ Million Dollar lawsuit against Toyota for reduction in Hybrid City fuel economy for the past 2 decades.

    Also a couple more graphic video updates to add to the information in this Thread:







     
    #114 TheLastMojojomo, May 5, 2024
    Last edited: May 5, 2024
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  15. Troy1994

    Troy1994 New Member

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    I think you mean something else, 17L/100km is very bad. Translates to 13 MPG. A good amount in l/km is around 5L / 4.8 /4.0 or lower. (49 mpg)
     
  16. Troy1994

    Troy1994 New Member

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    I’ve disconnected it only twice, but I only notice a small drop. It gets better over time.
    Since I’m in the EU I can force the car into EV mode if I wanted to. Maybe there’s a difference in US / EU versions. Mine is an 08 with no SKS. Your claim that most prii don’t have SKS is not totally true.
    Other than that I just drive the car. Trying to completely debunk the car’s computers and complex coding is something only Toyota tech could do I think. But hands down for doing so.

    I think that most people don’t even notice it. The car does whatever it wants to do haha.

    Edit:
    You claim that you can accelerate “aggressively” from 0 to 40mph on just electric power. That’s 64km/h. Now, how is that possible? If you do it “aggressively” (flooring or harsh acceleration), the engine comes on.
    Now I’ve only encountered that twice. Once when I was accelerating very slowly behind a lorry. Managed to get up to 66 km/h.
    The other time was after the light turned green when I approached it, so not from a full stop. Did somewhat the same thing.

    But if you move off quick, how can you ever achieve that? Even in EV mode, (I have EU Prius) it turns off when going past the limit of 45 km/h or when requesting more power.
    I find that hard to believe. I can try it on mine though.
    The bat on mine is usually at the highest blue bar. Occasionally goes to a green status.
     
    #116 Troy1994, Jul 12, 2024
    Last edited: Jul 12, 2024
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  17. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    DarkAlaranth said:
    Hmmm. I have no data, but I suspect my Prius is in a High state, as it's getting 17Km/l (Worked out by distance travelled/liters refilled) which I believe is just under 40MPG

    No, you're misreading: he says (and means I'm sure) 17 kms per liter, not liters per 100 kms.

    It's a measure not normally used in North America, similar to miles per gallon. It converts to roughly 5.9 liters per 100 km, and 40 mpg US (as he says).

    convert km per liter to liters per 100km - Google Search

    convert km per liter to mpg us - Google Search
     
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  18. Troy1994

    Troy1994 New Member

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    Aaah I see! Thanks for the clarification. I genuinely thought he meant the other thing. It’s roughly like how we say it here (Netherlands) (1 op 23) (1 on 23).
    That explains it, since I’ve never really seen someone using that form.
     
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  19. dolj

    dolj Senior Member

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    km/L is used in Japan and South Africa and maybe other places. I prefer L/100 km as it is a linear scale. MPG and km/L are the inverse scales and are not linear.
     
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  20. Troy1994

    Troy1994 New Member

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    Did not know that, thanks. I prefer l/100km too.
     
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