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2008 Fuel "Gauge" Display

Discussion in 'Gen 2 Prius Technical Discussion' started by Christov Tenn, Feb 22, 2020.

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  1. Christov Tenn

    Christov Tenn Junior Member

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    Consistently the 2008 Prius (purchased early December 2019) fuel 'gauge' displays 2 blocks with about 230 miles driven after a fill-up. Surely the range on this car at even 40mpg is greater than about 300 miles?

    I've "reset" the gauge using the popular YouTube method - Trip A, foot on brake-hold odo-power on x2, release odo, press odo x3 holding on third depression, six digits appear-release odo, press and hold odo until third digit changes to 1. Done this two, maybe three times without any apparent change in the gauge's behavior.

    Is it possible the fuel bag has some kind of problem that's diminished the amount it will hold?
     
    #1 Christov Tenn, Feb 22, 2020
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  2. fotomoto

    fotomoto Senior Member

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    Happens more in winter as the cooler temps kept the bladder from fully forming during refills. Should get better come spring.
     
    #2 fotomoto, Feb 22, 2020
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  3. Christov Tenn

    Christov Tenn Junior Member

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    I hope you're right.
     
    #3 Christov Tenn, Feb 23, 2020
  4. fuzzy1

    fuzzy1 Senior Member

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    This seems to be a fairly common problem with the fuel bladder in American Gen2s. There was very good reason why this feature was not carried on to subsequent generations.
     
    #4 fuzzy1, Feb 23, 2020
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  5. Christov Tenn

    Christov Tenn Junior Member

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    This morning with about 220 miles on the odo, I was only able to add about 3.7 gallons of fuel, and even this left the "gauge" one block short of indicating "full." Hopefully warmer weather will cure this problem. Noted in the yard, the first hyacinth has bloomed. Spring's not far off.
     
    #5 Christov Tenn, Feb 23, 2020
  6. fuzzy1

    fuzzy1 Senior Member

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    This is another face of the bladder problem, and I experienced it in a rental Gen2 before buying my first Prius, a Gen3.

    There are numerous threads here (all old now) about the various measures Gen2 owners took to get around this premature pump shutoff and get the bladder closer to full.
     
    #6 fuzzy1, Feb 23, 2020
    Last edited: Feb 23, 2020
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  7. edthefox5

    edthefox5 Senior Member

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    Vent the gas tank. When u go to get gas take the gas cap off and let it vent for a while, it will relax the bladder and help with the shut off and the gas belching.
     
    #7 edthefox5, Feb 23, 2020
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  8. Christov Tenn

    Christov Tenn Junior Member

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    Thanks for your responses. I've looked up several of those old threads. One in particular from 2008 where the OP, named DAR, complained of this problem with her new (then) '08 Prius. It struck me as odd that a number those who replied to her message expressed disbelief that she thought it important to have some idea of her vehicle's range. Today's schedule involves a 160 mile roundtrip and my vehicle's gauge displays four blocks. I will try venting the gas tank before filling today and the temps are supposed to get into the 50s, so maybe will have a better experience than last.
     
    #8 Christov Tenn, Feb 25, 2020
  9. ydpplqbd

    ydpplqbd Active Member

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    I agree completely with regard to knowing range and distance to empty ("DTE"). The only good result of the fuel gauge uncertainty is that I have been forced to keep meticulous records at every fillup. Until I get this fuel gauge recalibrated properly, I estimate DTE at every fillup (by multiplying fillup gallons with average mpg for last five fillups). I have never been stranded using this methodology over about 25 fillups. With that said, I will likely be recalibrating the fuel gauge (using instructions by a contributo ron another thread with last name "Angles") at the next fillup. Hopefully, I will be able to rely on my fuel gauge in the future.
     
    #9 ydpplqbd, Feb 25, 2020
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  10. Christov Tenn

    Christov Tenn Junior Member

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    Today's schedule was met using my '04 XC70 because my '08 Prius was dead. Got a new starter battery on the way home. Fill up will have to wait.

    Range of the XC70 is about 500-520 miles mostly highway; vehicle uses premium fuel. When it's parts are harmoniously aligned, which is most of the time, it's a joy to drive. An expensive joy, but a joy nonetheless.
     
    #10 Christov Tenn, Feb 25, 2020
  11. Christov Tenn

    Christov Tenn Junior Member

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    Ok. This morning filled up about 10 am. Outside temperature was 55 degrees, F. I'd driven 184 miles since last fill up (filled up when the gauge showed two blocks). Today from around three blocks on the gauge, the tank took 6.12 gallons of fuel. I allowed the tank opening to "breathe" for a couple of minutes, then, twice toward the end of the fillup, shoved the car to rock it, some. It accepted more fuel, although at one point, the tank "barfed" some fuel out when I completely removed the nozzle (spilled on my Keen knock-offs). Added a little more fuel and kept the nozzle in place with gap for air and it burbled for about 2 minutes. After that, it took some more fuel.

    Fuelly informs me I got 30.1 mpg, although this is inaccurate as the fuel-bag capacity seems to vary, as noted previously, depending on variables that include ambient temperature.
     
    #11 Christov Tenn, Mar 1, 2020
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  12. ydpplqbd

    ydpplqbd Active Member

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    A week or two ago, I intended to re-calibrate my fuel gauge using methods set forth on an older PC thread. See: Fuel Gauge calibration | PriusChat However, on the tank of fuel before the most current tank of fuel, I accidentally hit the fuel mpg monitor reset button on the MFD at almost the same time as last blin (AKA pip) started flashing. After I fueled up a few miles later (which I would describe as my current tank of fuel), the gas gauge began to act in a way more consistent with the fuel pumped into the tank. At the last fillup, I pumped 9.263 gallons into my tank. Which means my distance to empty (AKA "DTE") is 463.15 miles (9.263gal x 50miles/gal=463.15miles). At halfway to DTE (namely, 223 miles) my fuel gauge now displays 5 blins (IOW, exactly half a tank). I will try this for awhile and see how the calibration versus DTE works out (currently at about 300 miles with two blin first displaying at about 285 miles). May take awhile as we are hunkering down in response to the realities around us.

    PS Alternative analysis is that last fillup on 70F day was the largest ever 9.263 gallons (by about 1 gallon over previous largest fillup) which somehow caused gas gauge to recalibrate.
     
    #12 ydpplqbd, Mar 26, 2020
  13. Christov Tenn

    Christov Tenn Junior Member

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    That's an interesting happenstance - reset with last block flashing. Temps are rising here, too. About 79 degrees today. My mileage has improved and the gauge seems to be functioning more as one would expect. I think my gas tank's bladder is expanding and filling better.
     
    #13 Christov Tenn, Mar 26, 2020
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  14. prius_nerd

    prius_nerd Junior Member

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    @ydpplqbd and @Christov, did you ever get this solved?

    I have tried the weird chicken dance from Rick Angles (Toyota Master Diagnostic Technician), and it didn't seem to resolve my problem.

    What do you think about fuel guage problem.... | Toyota Prius Forum

    Also, ChatGPT says the following (which could be completely false):

    There is no specific method to recalibrate the fuel gauge on a 2008 Toyota Prius, as the fuel gauge is electronically controlled and its readings are processed by the vehicle's computer system. However, here are a few steps you can take to check if there is a problem with the fuel gauge:

    1. Check the fuel level: Make sure that the fuel gauge is actually reading inaccurately by checking the fuel level with a separate measuring device, such as a dipstick.
    2. Check the fuel sender unit: The fuel sender unit is located in the fuel tank and is responsible for sending a signal to the computer indicating the fuel level. If the sender unit is faulty, it can cause the fuel gauge to read inaccurately.
    3. Check the fuel gauge wiring: Wiring issues can also cause the fuel gauge to read inaccurately. Look for any broken, frayed or corroded wires in the fuel gauge circuit.
    4. Check the computer system: If you have ruled out all of the above, there may be an issue with the vehicle's computer system. A diagnostic scan of the computer system can be performed to determine if there are any error codes related to the fuel gauge.
    If the problem persists, it is recommended that you have the vehicle inspected by a professional mechanic to diagnose and fix the issue.
     
    #14 prius_nerd, Feb 12, 2023
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