Acting like a manual trans - engine connected directly to wheels

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Wecandothat4u, Mar 3, 2025.

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  1. Wecandothat4u

    Wecandothat4u Junior Member

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    We replaced the engine and trans last year and have put on 6524 miles since then.

    First indication of a problem was jerky backing up. Then had to reboot to get the engine to run. Within a few miles even that would not work. No engine run.

    All fuses checked good. Heavy duty fuse bar looks good.

    Engine won't start. Battery will move it forward but not so good backwards. When moving forward, the engine turns like it has a manual trans in gear with the clutch engaged. When in neutral we push the car and the engine turns a bit.

    There is a long story leading up to this , but the realization of the connection between the engine and wheels seems like the most important part right now.

    The inverter coolant disappeared. I discovered this soon after the failure.

    Codes through the process have been: P3190, P0031, C2310, C2318, B1826, C1259, C1310.

    We have replaced the Inverter and the HV Battery. No joy.

    Ready light has been working but the power button will not go green with the foot on the brake. But green if we don't press on the brake.

    Full disclosure. I've been driving with the red triangle on all the time. I can reset the screen, but get the P lock notification every time I stop. Car was working and I needed it for work, (I deliver packages for USPS) so I didn't pursue those problems.

    Normally I would just replace the car. I buy them cheap, remove everything but the driver's seat and run em until dead, but this one is blue and I just fancied it up with stars and stripes and I'd like to keep it going.
     

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    #1 Wecandothat4u, Mar 3, 2025
  2. ChapmanF

    ChapmanF Senior Member

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    Are you saying "the crankshaft wiggles a little when we start pushing the car in neutral", or "the crankshaft turns and keeps turning for as long as we push the car in neutral"?

    This is a transmission that depends completely on the HV control ECU taking electrical control of the motor-generators in order for any significant torque to get through from the engine to the wheels or vice versa. If you showed the transmission to a mechanic who didn't get the roles of the MGs, the mechanic would say "what is this, a joke? it's always in neutral! (when it isn't in Park)".

    A little wiggle of the crankshaft as you start pushing wouldn't totally surprise me; MG1 will freewheel as you push, but there's some mass and inertia to it.

    If you keep pushing and the crankshaft keeps turning, though, you've got a transaxle with something mechanically fubared inside.
     
    #2 ChapmanF, Mar 3, 2025
  3. Wecandothat4u

    Wecandothat4u Junior Member

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    You got me thinking so we lifted the front end and it started right up and spun the wheels. Step on brake and kill the engine. So it is definitely locked up inside. No way that could be a control issue, right? Something mechanical locked up inside. Wondering what might cause this.

    I guess it's time to pull the engine/trans and see what is going on.
     
    #3 Wecandothat4u, Mar 3, 2025
    Last edited: Mar 3, 2025
  4. ChapmanF

    ChapmanF Senior Member

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    metal fragment lodged in the PSD teeth, I'm imagining
     
    #4 ChapmanF, Mar 3, 2025
  5. MAX2

    MAX2 Senior Member

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    What is the condition of the oil in the gearbox with MG?

    And is there any there at all?
     
    #5 MAX2, Mar 4, 2025
  6. turbo5spd-prius

    turbo5spd-prius Junior Member

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    Yeah, toyota says you don't need to change the trans fluid so some people don't. It's a LIE, LOL. If you have a lot of miles (over a hundred k) you need to change it. Probably change it at least every hundred k. Mine acted up around 160k, being jerky on accelerating from stops so I changed the fluid and the problem went away.
     
    #6 turbo5spd-prius, Mar 4, 2025
  7. ChapmanF

    ChapmanF Senior Member

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    The transaxle on this car was installed 6524 miles ago.

    I'm allowing myself two guesses about the transaxle that was installed then:

    1. it wasn't new
    2. it wasn't undamaged
     
    #7 ChapmanF, Mar 4, 2025
  8. MAX2

    MAX2 Senior Member

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    Let's add a couple of options:
    3. Another oil was poured into the box, which is not recommended.
    4. No oil was poured into the box, leaving the old one
     
    #8 MAX2, Mar 4, 2025
  9. Fred_H

    Fred_H Misoversimplifier

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    Yes, and one other possibility is that MG1 is seized, which would have the same effect, but with a higher gear ratio.
     
    #9 Fred_H, Mar 8, 2025
  10. ChapmanF

    ChapmanF Senior Member

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    MG1 does the starting, so had to move for that to happen.
     
    #10 ChapmanF, Mar 8, 2025
  11. Wecandothat4u

    Wecandothat4u Junior Member

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    I've been waiting for access to the lift in my friends shop. Finally got it. The trans was toast. Lots of metal around the drain plug. Got another trans from the wrecking yard. Works fine...

    BUT, after two engines and three transmissions, I still get the P Lock message.

    On a side note, I think I need to replace the inverter coolant pump. Fluid doesn't flow when trying to bleed it into the tank.
     
    #11 Wecandothat4u, Apr 5, 2025
  12. Wecandothat4u

    Wecandothat4u Junior Member

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    Oh. And present codes are:
    P0031.
    C2310
    B1826
     
    #12 Wecandothat4u, Apr 5, 2025
  13. Wecandothat4u

    Wecandothat4u Junior Member

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    Won't go into neutral in accessory mode.
     
    #13 Wecandothat4u, Apr 5, 2025
  14. ChapmanF

    ChapmanF Senior Member

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    "Accessory mode" is one button push, no brake. Radio/MFD work, rest of dash is off. It's normal for the gear selector to have no effect in accessory mode.

    "IG ON" mode is two button pushes, no brake. Whole dash lights up, but not the word READY. You should be able to shift to neutral in IG ON mode.
     
    #14 ChapmanF, Apr 5, 2025
  15. MAX2

    MAX2 Senior Member

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    What oil was used?
    Have you disassembled the transmission to find out the cause of the failure?
     
    #15 MAX2, Apr 6, 2025
  16. MAX2

    MAX2 Senior Member

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    Important error with code C2310.
    The auxiliary battery voltage is constantly applied to terminal BATT. The terminal BATT voltage is used to
    power the transmission control ECU memory. The transmission control ECU outputs this DTC when it detects a malfunction related to terminal BATT.
    A faulty fuse may also be the cause.
    Check according to the attached manual.

    The third B1826 is for a faulty squib, and has nothing to do with the transmission.
     

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    #16 MAX2, Apr 6, 2025
  17. Wecandothat4u

    Wecandothat4u Junior Member

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    Okay. I misspoke. Won't go into neutral in IG ON mode. We want to do that to bleed the coolant system.
     
    #17 Wecandothat4u, Apr 6, 2025
  18. Wecandothat4u

    Wecandothat4u Junior Member

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    Oil is Valvoline full synthetic max life multi-vehicle. It claims to be okay for Toyota WS.

    I just turned the trans in for the core charge.
     
    #18 Wecandothat4u, Apr 6, 2025
    Last edited: Apr 6, 2025
  19. Wecandothat4u

    Wecandothat4u Junior Member

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    Went for simple/easy and swapped out the Trans ECU. No joy. However, supplying 12 V directly to the wire leading into the Trans ECU solves the problem. So now all we need to do is figure out where the disconnect is. We have the wiring diagram but do not know where those connections are.

    So can anyone help us with physically where to look?
     
    #19 Wecandothat4u, Apr 7, 2025
    Last edited: Apr 7, 2025
  20. Wecandothat4u

    Wecandothat4u Junior Member

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    Finishing up on the inverter pump part of this thread, we replaced the inverter pump and it now bleeds fine. I was blown away at the price differences for the pump.
    Napa over $300
    O'Reilly's over $200
    Amazon. About $23
    The one out of my parts car. $0. But it didn't work so we went with the one from Amazon.
    Thinking that the bad pump might have something to do with why the coolant disappeared. Got hot and evaporated? Opinions?
     
    #20 Wecandothat4u, Apr 7, 2025
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