Catastrophic motor/generator failure? Pulsating noise under heavy acceleration followed by death

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by anonymous, Dec 5, 2022.

  1. anonymous

    anonymous Member

    Joined:
    May 18, 2015
    150
    90
    0
    Location:
    US
    Vehicle:
    2011 Prius
    Model:
    II
    we were on a road trip when I started experiencing a strange noise under heavy acceleration. i did go a long way since the first symptom cause it was all flat, but then mountains halfway through forced the noise to occur, and then the car shut down with "check hybrid system". First scan revealed P0A4B "Generator Position Sensor Circuit" and P0136 #2 o2 sensor circuit, then second scan additionally reported P0102 MAF circuit low, P0031 #1 o2 heater circuit low; third scan found P0113 intake temp sensor circuit high.

    At first I thought it was a probably-harmless exhaust leak cause there was already a leak at the flange due to restricted cat, also have been living with P0139 cause the anti-P0420 spacer is sooted up. So when it died I thought maybe exhaust gasses burned some wiring. But an inspection of whatever I could inspect (i took the windshield wiper stuff and air box out) revealed nothing whatsoever. And nothing made any sense.

    But after some analysis I think I know what happened. The motor/generator unit, with 283k miles of strenuous use, has developed play in its bearings, and under torque of heavy acceleration, a rotor has started rubbing its stator, making that loud pulsating noise. And I guess it destroyed its position sensor which messed up the computer. The codes indicating broken circuits for #2 o2, #1 o2 heater and maf+air temp don't make sense. But I guess sometimes collateral red herring codes happen?

    Do you think this is right? With that noise I am pretty confident it was a catastrophic failure and don't think it is worth it to get a diagnosis. I think the MG assembly may need to be replaced, and the annoying thing is that the engine also has oil burning issue and dead cat and leaks and stuff so, it ought to be replaced too. The whole damn powertrain!

    What do you suggest we do with it? I think it's gonna be super expensive to have it professionally repaired and we'd be better off swapping with another used prius or something. Maybe I could take my time and DIY swap the powertrain assemblies if I could source good replacements. But I don't know if I'll be in the mood for that sort of thing anymore. I might prefer to just have it sold as-is :/

    I'll try to post a clip of the sound later.
     
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    19,355
    12,925
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    The position sensor isn't embedded near the stator where you suspect rubbing; it's on the end of the shaft (in the end plate for MG2, less accessible inside the transmission for MG1). If you search around (use the term 'resolver' rather than 'position sensor'), you should be able to find some pictures and videos that show where.

    I would look carefully at the wiring and connectors before drawing dire conclusions about stuff that's well-protected inside the tranny. A bad connection in the wiring to the resolver is more than enough to throw things off.

    You have several other codes that could be brought on by wiring problems too (in different circuits). Is it possible rodents are involved? They sometimes disregard the color codes and chew on circuits that aren't closely related.

    The resolver signal is very critical to keeping the magnetic fields in the MG synchronized to the rotor position, and a pulsating noise wouldn't surprise me if that synch was off (though I more expect the ECU to simply say "bad resolver signal, I can't do this" than to try to muddle through).

    While looking at the electrical connections to the resolver is fair game, avoid loosening any of the bolts used to adjust it. The adjustment at the factory is critical, and there are no published instructions for doing it in the field.

    Another issue that can cause a pulsating noise is a short in a stator winding. The rotor uses permanent magnets, and if there is a shorted loop in a winding, current will always be induced there as the rotor poles go by; nothing can stop it. That would be another condition requiring replacement, but for a different reason than bearing wear.
     
  3. anonymous

    anonymous Member

    Joined:
    May 18, 2015
    150
    90
    0
    Location:
    US
    Vehicle:
    2011 Prius
    Model:
    II
    Here's a couple clips showing the noise
     
  4. anonymous

    anonymous Member

    Joined:
    May 18, 2015
    150
    90
    0
    Location:
    US
    Vehicle:
    2011 Prius
    Model:
    II
    How could I get a wiring diagram to maybe try and figure out the common denominator of all these electrical errors?
     
  5. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    19,355
    12,925
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
  6. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    8,773
    3,597
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    The symptoms you're describing isn't a failing motor generator, but the car going into safe mode to protect itself from something going wrong in the hybrid system.

    Furthermore, because you failed to spend a couple hundred dollars and less than 2 hours of work replacing your clogged catalytic converter your flange gasket failed where cat connects to exhaust header which has been blowing hot exhaust gas into your engine compartment which not only makes a huge mess but starts melting electronic parts. I replaced a valve cover gasket for someone who thought they could ignore their clogged cat that blew out the flange gasket once. It was a huge nasty mess and entirely his fault for failing to repair a simple problem before it turned into a more major problem.
     
Loading...