Grinding noise, after “battery low voltage” warning. When engine started.

Discussion in 'Gen 4 Prius Technical Discussion' started by Brandon Kennedy, Nov 18, 2019.

  1. Brandon Kennedy

    Brandon Kennedy Junior Member

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    Hello! I haven’t been on here in a few but I’m back.

    my Prius now has 90k miles on it. I went to the car wash, left it in whatever mode it is before you do ready, pressing the start button two times but no foot on the break, just so I could crack all my windows and clean them... so car probably sat in that mode maybe 10-20 mins. I get in, go to start it, and it says battery low voltage... I was like great!

    I knew the Prius had a weak 12v (from reading) and also seeing it’s only 295cca or something around that. But I figured well it didn’t turn anything off so I’m sure it’s fine. Figured being a new car it would have 12v protection but I was wrong... tried to press the brake and start it three times and nothing. Not even a click, just turned all the dash lights n stuff on for the split second to try to start it...

    So I stopped and let it sit for about 5 mins to let the voltage in the battery build up for a second... went to start it, and woala! The green ready light came on and it started the engine for a split 15 seconds lol, I was like well at least it’s going again.

    It didn’t make the noise then, it made the noise the 2nd time it started! And I have NO IDEA what it was. I figured well maybe the 12 volt was low enough to where it tried to grind the “starter” and start it a 2nd time because it didn’t think it started the first time. I don’t know if that’s even possible for it to think that, but it basically sounded like the engine was grinding against the flywheel, or the axle spun... as in like definitely metal on metal noise... it hasn’t done it anymore on anymore starts since then, but I do wonder if anyone has any clue what that could of been or why it happened?
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    Actually - there is no starter. The MG1&MG2 work to do the driving, starting, generating etc.
     
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  3. Brandon Kennedy

    Brandon Kennedy Junior Member

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    right. That’s why I put starter in quotations. I couldn’t remember what the terms were for the generators lol. I know their not called that either I’ve lost my mind haha.

    any idea what you think could of caused it??
    What is extremely weird is I watched the Weber video on the charging system and see that it normally puts a 13.8-14.1v charge into the battery all the time, so I wonder why mine didn’t? Unless it’s because I didn’t have it in ready mode and instead had it in (press start button two times) mode lol. I know it says what the mode is I just don’t wanna to out to my car, it’s cold lol.

    I’ve been having the axle clicking noise since I got the car at 62k miles, driver side was replaced under warranty by 1st owner... I haven’t dealt with replacing the other because it’s out of warranty and doesn’t cause any problems other than clicking...

    this is a great time when I wish I would of had my audio turned on with my dash cams :/ but oh well... it didn’t make it on take off, started off in EV mode (not the actual mode but you know the electric motor pulling me) and then the engine came on and right as soon as it did I let off the gas because it made a god awful metal on metal grinding horrific noise.... and then it never did it again all the way home... but remember this was after it had already started once from leaving the car wash, then I stopped at the stop sign and it did it basically right after take off around 6-10mph... it literally sounded like when you hit the starter a 2nd time in a car after it’s already started.
     
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  4. booke02

    booke02 Active Member

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    I may be wrong, but I thought that the 12V battery was only used for the electronic systems: the HV battery is used to start the engine.
     
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  5. Elektroingenieur

    Elektroingenieur Senior Member

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    That’s it exactly: if the car is off, or in ACCESSORY or (Ignition) ON mode—in other words, in any condition but READY mode—the system main relays at the HV battery are open, so the DC-DC converter has no power source from which to energize the 12-volt bus or charge the auxiliary (12-volt) battery.

    The Owner’s Manual (PDF, always warm at Toyota.com) explains the modes on page 227.
    I’m not sure what this might have been. Are there any other signs of trouble?
     
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  6. alanclarkeau

    alanclarkeau Senior Member

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    Just as an aside - I had a flat 12v battery, I think over 12 months ago (operator error, I'd left the car open, and some lights on). But I left it for an hour or 2 to revive, and it worked fine again - and has ever since. BUT - there was no grinding noise, so sorry, no idea.
     
  7. kithmo

    kithmo Couch Potato

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    I think he's saying the car didn't go into ready mode, "just turned all the dash lights n stuff on for the split second to try to start it..." not enough power in the 12v to energize the HV battery relays.

    Brandon, I think it does have 12v protection, ISTR reading somewhere that, in acc mode, the car switches itself off after a certain time (20 or 30 minutes was it ?) to prevent the 12v dropping too low to go into ready mode. So it seems you may have a weak 12v. Depending on use, i.e. leaving it in acc mode often or infrequent or short journeys, it may be worth may be worth charging the battery up now and again on a trickle charger/conditioner, if none of that applies then the 12v probably needs replacing. I do with mine every 5-6 weeks because I do less than 3K miles a year and mainly short runs.
    I've no idea what the grinding could be, are you sure it's a grinding noise and not a relay buzzing due to low voltage.
     
  8. bisco

    bisco cookie crumbler

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    i hope the 'grinding noise' wasn't gen3 cold start knock :eek:
     
  9. Brandon Kennedy

    Brandon Kennedy Junior Member

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    I don’t think it was the motor knocking at all. It was definitely something spinning. It almost sounded like the tire spun but a metal on metal noise, but like fast and went with the engine speed. Which makes me think either axle, but I haven’t seen anyone talk about it other than the clicking on regen, and I’m not hard on the car. I don’t think this car has a flywheel, but it’s almost like it tried to start itself a 2nd time when the engine was already started. That’s the only way I can really describe it. It still hasn’t done it anymore since then but still weird for it to occur.
     
  10. bisco

    bisco cookie crumbler

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    There is a one way safety clutch between the engine and tranny. Maybe it spun a little
     
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  11. alanclarkeau

    alanclarkeau Senior Member

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    My experience (in the Last Post) is that not everything turns off. I know my taillights were on while the car was off, and they didn't turn off. I was made aware when a neighbour knocked on the door to tell me my lights were on. I don't recall which others were.

    I thought it was odd - as my KIA 10 yrs earlier did turn everything off (at least I think it did - it definitely turned the interior light off in 20 mins - I tested it!!).
     
  12. kithmo

    kithmo Couch Potato

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    What I really meant to say was that it kicks you out of ACC mode after the allocated time.
    The interior lights do turn off after 30 minutes if you leave the switch in the on position with the car totally off.
    The tail lights and front parking lights will stay on indefinitely if left on when the car is off so you can park in areas where parking lights are required.
     
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  13. alanclarkeau

    alanclarkeau Senior Member

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    Ahh - that's probably what I did. I think it was off. I must try againo_O.
     
  14. dald

    dald New Member

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    Drain your HV battery till the ice kicks in to recharge. Accelerate gradually from stop. Check if you hear the same grinding sound as the car speeds up.

    I had the same issue on a second hand I was testing the other day. Wasn't sure whether it's the CVT or engine as it's only replicable when HV battery is drained and ice had to do most of the work between 8-25km/HR


    Posted via the PriusChat mobile app.
     
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