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Stuck in regen mode?

Discussion in 'Generation 1 Prius Discussion' started by elendilmir, Aug 6, 2013.

  1. elendilmir

    elendilmir Member

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    I've got a 2002 with 159K miles, a Reinvolt battery and a power steering problem that leaves me with no power steering and a perpetual warning on the main display.

    I had 4 new tires put on the car recently. Since then, I have gradually started noticing a humming noise. I can't tell if it is just the new tires "singing", or if the car is stuck in regen mode. The car "feels" normal, and if I drop it into B I can feel a slight difference. I can't see if it is moving electricity to the battery because of the PS warning on the display.

    I have a scanguage II. Is it possible to see if the car is stuck in regen with it?
     
    #1 elendilmir, Aug 6, 2013
  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The problem with a "humming" noise is if it is speed dependent and exists even if rolling and shifted into "N" it is the signature of a failing MG2. The definitive test is to add the XGAUGE definition for MG1 and MG2 temperature. In normal operation:

    ICE_temp > MG1_temp > MG2_temp​

    When MG2 develops a shorted winding:

    MG2_temp >> ICE_temp > MG1_temp​

    If you see MG2_temp greater than 100C, the boiling point of water, it is toast and needs to be replaced or repaired in the next month or so. But first, diagnose the problem.

    Bob Wilson
     
    #2 bwilson4web, Aug 6, 2013
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  3. elendilmir

    elendilmir Member

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    I'll try shifting it into N over lunch and see if that sound continues. I can confirm that it IS speed dependent though <<wince>>.

    edit: The MG2 is also called an "electric assist motor", correct? I have been doing some google-fu looking for good deals. I'm seeing them for $400 to $600 on ebay.
     
    #3 elendilmir, Aug 7, 2013
  4. ChapmanF

    ChapmanF Senior Member

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    Well, MG2 will produce that symptom because it is one of the things that always turns when the wheels are turning, and always in the same ratio to wheel speed. But there are other things of which the same can be said ... wheel bearings, for example. So knowing only that there's a speed-dependent sound that continues in N, there is a set of possible causes needing to be explored.

    High MG2 temps would be further evidence pointing to MG2. Also, it might be possible to distinguish an MG2 problem from a wheel bearing problem by the pitch of the sound (my issue turned out to be wheel bearing). My bearing issue was also easily confirmed by jacking up the affected corner and turning the wheel by hand.

    Mine was the right rear and went at about 160,000 miles.

    -Chap
     
    #4 ChapmanF, Aug 7, 2013
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  5. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    Yeah, my first suspect would def be wheel bearings. My left rear wheel bearing gave out at 96,000. Make sure you check this out before spending $4-$600 on an MG.
     
    #5 usnavystgc, Aug 7, 2013
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  6. elendilmir

    elendilmir Member

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    Learning all kinds of stuff about this scanguage! I took it out for 4 miles over hills at 40 mph. the mg2 temp was 125 f. How long should it take to get hot if it is the traction motor and not bearings?
     
    #6 elendilmir, Aug 7, 2013
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Good deal, 125F is NOT a problem. If it were 125C, there would be a problem. When MG2 fails, the temperature rise is very quick. This is why it is so important to have a Prius aware scanner.

    I like the idea of lifting the car so the wheels turn freely and find which one 'rattles.' You might also feel the hubs after driving around to see if one is hotter than the others.

    Bob Wilson
     
    #7 bwilson4web, Aug 7, 2013
  8. Jeff F

    Jeff F Member

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    Doesn't sound like it's the transmission, thankfully. It could also be tire noise -- not likely, but it's possible that one of your new tires has a defect. I went through this with my Kia recently - after an alignment I started noticing a speed-dependent roar that sounded like it was coming from the right front side. First I rotated the tires, and nothing changed. Then I jacked up the front of my car and turned/wiggled each wheel by hand, but couldn't really find anything amiss. Finally I tried putting the car in gear with one front wheel off the ground. Bingo. All quiet with the left front wheel rotating, but a roar from the right front wheel when rotating. I've ordered a new bearing.
     
    #8 Jeff F, Aug 8, 2013
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