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ICE running, lost drive power

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by James_D, May 18, 2023.

  1. James_D

    James_D New Member

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    My 2008 Prius with 190k miles left me stranded for the first time. I was less than a mile from home when the car stated acting erratic when accelerating from a stop. It felt like a bad CV axle in a FWD car. I attempted to turn the car around but got stuck in the depression at the end of a neighbors driveway. When I tried to accelerate the traction control light would come on and the car would make a vague clicking/grinding sound but couldn't make it out of the depression at the end of the driveway. We had to push it out of the way and have it towed.

    The mechanic drove it around their lot fine later on but just texted me to say that it seems to drive only under battery power but that the engine isn't engaging. I live in a small town and the mechanic isn't a hybrid expert but he theorized that it may be a clutch connecting the ICE to the drivetrain. I've searched the forum and I keep seeing a post saying that there's "nothing to slip" but since the ICE can be running when the car isn't moving there must be something that engages and disengages the motor from the drivetrain. Could it be the Damper PN: 31270-47060 or is it more likely to be something else?

    This is my first post, any help is appreciated, thank you in advance. Although I'm relatively knowledgeable about ICE cars I don't know enough about Prius to know what else to search for.
     
    #1 James_D, May 18, 2023
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    Hello and welcome to PriusChat!

    The transmission on a Gen2 Prius is a planetary gearset, which has 3 "elements". If you control rotation of any 2 of those elements, you manipulate the 3rd.

    Each of those elements is connected to different things. One goes to a motor (MG2) plus the differential and drive axles to the front wheels. One goes to another motor (MG1). Last one goes to the ICE.

    If the car is in park (MG2 is held immobile by the parking pawl) and the hybrid ecu wants to start the ICE- it commands MG1 to spin (as a motor) which drives (rotates) the ICE through the gearset.

    Once the ICE is running, MG1 must still spin, but now it's driven by the ICE as a generator to charge the HV battery.

    When you drive in "EV" mode (at low speed), MG2 is used to provide torque to turn the drive wheels. The ICE is stopped, so MG1 has to spin "freely" to permit MG2 rotation.

    The ecu is the orchestra conductor, blending MG2, MG1, and ICE to achieve the immediate goal (moving the car, charging the battery, max MPG, min emissions, etc)

    Now to your problem. I assume at this point that when going "ready" - the ICE doesn't spin?

    The damper is kind of looks like a clutch disc and secures to a "flex plate" on the ICE crankshaft. The damper has a spring loaded hub to smooth out power pulses. The trans has a splined input shaft that engages the center of the damper hub.

    There have been cases where the input shaft has broken off- resulting in no ICE operation. Also the damper springs can fail (not sure if that would cause complete failure).

    The damper does have a friction disc (like a clutch disc) that's clamped in place. I have read that it's supposed to be able to slip if "excessive torque" is applied (?), but I have never heard of that happening.

    There's a little access plate at the bottom of the trans bellhousing. I would remove that plate and use a videoscope up into the bellhousing. Try to see if anything's broken, watch while using a socket wrench to turn the crank pulley bolt.

    Don't drive EV- at some point you'll discharge the HV battery and then it can be difficult to find any way to charge it. (There's $$$ "grid" chargers that can do it, or $ DIY methods if you have the know how).

    Posted via the PriusChat mobile app.
     
    #2 mr_guy_mann, May 18, 2023
    jerrymildred likes this.
  3. JC91006

    JC91006 Senior Member

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    Make sure you didn't run out of gas, if it's showing 2 or 3 bars remaining, I would add a couple gallons in just to make sure the gauge is not wrong.
     
    #3 JC91006, May 19, 2023
  4. James_D

    James_D New Member

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    I'll cruise over to the shop and will double check but I'm pretty sure the ICE motor was running/burning gas which would mean MG2 works and no broken input splines since MG2 would have to start the motor. I had my 7 month old baby in the car so it was a little frantic during the break down. I just wanted to get him out of the car to safety since it wasn't in a safe spot.

    I will also see if the battery is charging if/when the ICE is running. I should be able to turn the heat up to make sure the car tries to start the ICE.

    Is there any chance that a damaged wheel speed sensor cause the car to be cutting the power to the wheels or applying brakes to them if the car thinks a wheel is spinning too quickly? There was no ABS light but there wasn't much distance traveled.

    I'll see if the mechanic can get a look into the access plate, too, that's a good piece of into, thank you! You've given me a couple things to check.
     
    #4 James_D, May 19, 2023
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    If the ABS or Traction Control are in active use, then the "slip" light on the dash will come on. I have not seen a wheel sensor cause (severe driveability) problems without setting a code.

    Not saying that's impossible, just haven't seen it before. A more typical fault would be corrosion under a sensor mount- causing a weak signal with false ABS activation as the car comes to a stop. Or incorrect tire size causing T/C to kick in at 50. A cracked tone ring (toothed wheel) on the outer CV joint will cause random weirdness - but not "disable" the car.

    If your car can fire up the ICE, then the transmission and damper are intact.

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, May 19, 2023
  6. sam spade 2

    sam spade 2 Senior Member

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    You NEED to get it to a hybrid shop.

    This could just be a matter of the HV battery getting weak enough so that it will still start the ICE but
    won't operate some other things right.

    Same for the 12 V battery.
    You can get that tested yourself.
     
    #6 sam spade 2, May 19, 2023
  7. ChapmanF

    ChapmanF Senior Member

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    Your reasoning is good there, though just for the record, the MG that starts the engine is MG1. (MG2 is directly connected to the transmission output, so it can't turn without moving the car.)
     
    #7 ChapmanF, May 19, 2023
  8. James_D

    James_D New Member

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    With regard to the suggestion of taking the car to a hybrid shop, I would rather learn more about this car from a supportive community since it has been otherwise great to own and will eventually probably be replaced with another one. Besides the only hybrid shop in a wide area is going to be the dealership and it's not going to be economical to bring my $1500 salvage car there.

    I went back and confirmed that the ICE is starting and running. This makes me feel like MG1 and the input splines and dampener must be intact. The tech said he took the car for a drive around the block and it runs fine at low throttle but stumbles on harder acceleration which is what I experienced. The whole transmission/motor/generator assembly is not very expensive on ebay ($200) but I saw a note saying it does not include the shift control actuator.

    I can't find an explanation of the function of the shift control actuator. Can anyone direct me to or provide an explanation of the function? Could this be causing an issue? I'm still waiting for him to scope the interior of the driveline assembly and see if anything is visibly broken. We can also check the battery condition. Thank you!
     
    #8 James_D, May 25, 2023
  9. ChapmanF

    ChapmanF Senior Member

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    "Shift control actuator" is a sesquipedalian name for the little motor that moves things in and out of Park. That's all it does.
     
    #9 ChapmanF, May 25, 2023
  10. mr_guy_mann

    mr_guy_mann Senior Member

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    Stumbles under harder acceleration- first thought is ignition problems. Plugs and/or coils. Should set a misfire code, but doesn't always do that. Or the MAF sensor elements are dirty.

    DSC_3227.JPG

    Posted via the PriusChat mobile app.
     
    #10 mr_guy_mann, May 25, 2023
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