Master Warning Light Comes On and Off

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by TheWiredWorld, Aug 19, 2015.

  1. TheWiredWorld

    TheWiredWorld New Member

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    I was driving earlier today and it flashed twice (about a second and a half each), and then didn't see it again for a few hours. I was going about 40 MPH at the time.

    I was driving somewhere else today and when I got to the 70MPH mark (really, between 60-70), it objectively increased in frequency. I searched google and these forums, and the closest thread I can find that shares my ailments was this one:

    Master Warning Light - Toyota Prius Forum : Prius Online Toyota Forums

    I strongly hope (as I'm not a wealthy person), that it is indeed oil - as someone described that at higher RPMs, it can trip some sensor. It DEFINITELY happened at higher RPMs. I checked the oil level through the dipstick, and though it seems to be of a good level, it's very faint - it's not dark AT ALL. Is this fine?

    Side notes of information: I just had the Coolant Flow Assembly replaced in it this morning (though all of this could completely be coincidence...it could also not be...).

    So in summary:

    Had the coolant flow assembly replaced this morning, a few hours later, I see the Master Warning Light flash for about 3 seconds total, then nothing for a few hours. I keep driving later in the day on the high way, and , once I get to the 60-70MPH mark, it increases in frequency of flashing about 4 fold, but never just remaining on. The center console only ever says "Problem".

    What do you think?
     
    #1 TheWiredWorld, Aug 19, 2015
  2. bisco

    bisco cookie crumbler

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    could be some air still trapped in the coolant. was that engine or inverter coolant flow assembly? probably worth going back and having it checked out.
     
    #2 bisco, Aug 19, 2015
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  3. TheWiredWorld

    TheWiredWorld New Member

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    That's the other possibility I thought of. Maybe they didn't bleed it properly. It's an independent garage that I do trust, but they don't have much experience with Prius. It was the Combustion side of things coolant flow assembly.
     
    #3 TheWiredWorld, Aug 19, 2015
  4. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Coolant system worked on today, then warning light comes on today? I may not be the sharpest knife in the block, but I see a correlation, lol.
     
    #4 Mendel Leisk, Aug 19, 2015
  5. bisco

    bisco cookie crumbler

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    yes, prius engine coolant takes a lot more care to bleed than most cars. i suggest you recommend the toyota technical manual to him, it has details for all prius service. if he isn't interested, i wouldn't go back. hopefully, a word to the wise is sufficient. for brake fluid bleeding, you need toyota tech stream software and a laptop.
     
    #5 bisco, Aug 19, 2015
  6. ChapmanF

    ChapmanF Senior Member

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    You've caught the crux of the matter right here. The lights and messages on the dash and console are not enough to identify your problem; they are not there for that purpose. They are only there to announce that there is a problem, so that you will read the diagnostic codes (or have them read) and they, and only they, will point you in the direction of finding out what is wrong with your car.

    That it has something to do with the coolant work is a reasonable hypothesis (but not ironclad; coincidences do happen). If it is the right hypothesis, the codes will confirm it. If it isn't, they will point another way. Speculating is never a real alternative to reading the codes. (Sometimes you'll get codes that are precise and definitive; sometimes they will be puzzling and you'll still get your chance to speculate ... but jumping straight to speculation without reading the codes? Not recommended, ever.)

    So ... how 'bout those codes?

    -Chap
     
    #6 ChapmanF, Aug 19, 2015
  7. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Or if not the coolant, maybe something they disconnected in the process, and neglected to put back, or just plain messed up.
     
    #7 Mendel Leisk, Aug 20, 2015
  8. TheWiredWorld

    TheWiredWorld New Member

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    Definitely gonna check it out tomorrow
     
    #8 TheWiredWorld, Aug 20, 2015
  9. Sistroe

    Sistroe New Member

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    Hey, exact same scenario happened to my 2009 Prius with ~130k miles that had the inverter pump and coolant flow control valve replaced a few days ago. Do you remember if it was just coolant not being bled properly?
     
    #9 Sistroe, Dec 18, 2021
  10. bisco

    bisco cookie crumbler

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    o/p hasn't been seen in 6 years...
     
    #10 bisco, Dec 18, 2021
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  11. ChapmanF

    ChapmanF Senior Member

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    You might want to look at post #6.

    Even if you were to find out what exactly the trouble was with the OP's car six years ago, the fastest way to a solution in your case is probably to focus on finding out what the trouble is with your car now.
     
    #11 ChapmanF, Dec 18, 2021
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