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Low oil pressure warning light and tone

Discussion in 'Gen 3 Prius Technical Discussion' started by Frogerelli, Nov 19, 2022.

  1. Frogerelli

    Frogerelli Junior Member

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    Hello, the 2010 Prius I have given my daughter has begun occasionally having the low oil pressure light come on when the engine starts after she has started the car. It lasts only a second or two then clears. It only happens when the car starts from cold.

    I'm using 0w20 oil, it is nicely golden in color and up to the max limit on the dipstick. The car has 102k miles. This initially began late last spring and I changed the oil and filter, learning the local shop had crushed the filter by screwing the canister on too tight, so I was careful not to do it when changing the oil myself. (The car in the background is my 2017 Prius, not the affected 2010 Prius.) The remainder of the summer went incident free, but now it is starting to do it again.

    Is the oil pump mechanically or electrically driven? I'm trying to figure out why initial pressure can trigger the low sensor with the oil level full and on level ground.
     

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    #1 Frogerelli, Nov 19, 2022
    Last edited: Nov 19, 2022
  2. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Try the Toyota filter next time?

    Is it consuming any oil, and what rate?

    Have you had it since new, know it's complete history?
     
    #2 Mendel Leisk, Nov 19, 2022
  3. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Ok, that, and pic: something is not adding up. No matter how tight you torque down the housing, it is not going to compress the filter half an inch. Maybe that filter is too tall? Or something's out of place inside the housing?
     
    #3 Mendel Leisk, Nov 19, 2022
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  4. Elektroingenieur

    Elektroingenieur Senior Member

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    It’s mechanical. Toyota writes in New Car Features (more info), “A trochoid gear type oil pump is driven by the crankshaft via the No. 2 chain sub-assembly (oil pump drive).”
    The Repair Manual gives inspection procedures for the engine oil pressure switch itself (“10 kΩ or higher” resistance with the engine idling; “Below 1 Ω” with the engine stopped) and for the lubrication system, with an oil pressure gauge connected in place of the switch.
    By “low oil pressure light,” do you mean the “Low Engine Oil Pressure” message on the multi-information display (Owner’s Manual (PDF), page 509)? If it’s actually a warning light, it might be one with a different meaning, explained on pages 496–500.
     
    #4 Elektroingenieur, Nov 19, 2022
  5. Frogerelli

    Frogerelli Junior Member

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    I can try again with a Toyota filter.

    It doesn't consume any oil; it has been about 4000 miles since the last change, no oil top ups, and the level is still at the top of the dipstick. No drips on the garage floor nor on the hinged oil pan access door.
     
    #5 Frogerelli, Nov 20, 2022
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  6. Frogerelli

    Frogerelli Junior Member

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    I'll change the oil again with a Toyota filter and look in the canister/housing.

    Thanks and I'll follow up.
     
    #6 Frogerelli, Nov 20, 2022
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  7. Grit

    Grit Senior Member

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    From the photo attached, looks like the oil change person put in the wrong size filter in. It’s severely shorter and wider causing the filter housing to twist one of the filter’s end. Trade the daughter in for not diy’ing.
     
    #7 Grit, Nov 20, 2022
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  8. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Yeah, with third gen oil filter housing, if you screw it in completely and torque it to spec'd 18 foot pounds, it's going to be a certain height. Now put a an impact on and manage to turn it another 1/2 revolution,, it's height is going to reduce another mm at most.
     
    #8 Mendel Leisk, Nov 20, 2022
    Last edited: Nov 20, 2022
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