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'02 Prius, Not starting, P3125 Code

Discussion in 'Generation 1 Prius Discussion' started by Jerry G., Oct 7, 2014.

  1. ericbecky

    ericbecky Hybrid Battery Hero

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    Time to backtrack your steps.
    Also perhaps try to figure out why things were hooked up incorrectly previously.
    Odd that you don't have any codes or light showing.
     
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  2. royfrontenac

    royfrontenac Member

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    Hi Jerry - let the car sit and charge up, use techstream to monitor the battery voltages and the state of charge. Let the battery state of charge get to 60 %(this will take quite a while. Check the position of the shifter, it appears to think it is in neutral. The key not coming out is telling you there is a problem with the shifter. Read the email I sent you re the key. Roy from canada
     
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  3. Jerry G.

    Jerry G. Junior Member

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    So I did double check my work and it is all hooked up correctly. The 3 Mg2 cables are secured and in their respective connections, the other two orange cables are plugged in correctly (they can only go in one place as they have slots). Some idiot before I owned the car screwed it up by trying to fix whatever, and didn't connect everything properly to the inverter which caused the P3125 code.

    I am thinking there is a problem with the shifting mechanism or the switches that tell the ECU what position the shifter is in. I did notice that when I unplug the key release solenoid and the car is on or running, when I move the shifter into drive or neutral, I get the message in the display "when in neutral the system does not charge the battery", but, when I plug the key solenoid back in, that message goes away. I've looked at the small schematic diagram in the manual but it really doesn't show what I need to see.
    Any input?
     
  4. Jerry G.

    Jerry G. Junior Member

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    Update:
    The car is running and driving. This is the painful part. Eric the battery guy said "time to retrace your steps". I slept on his words just as I was taught as well by my dad "if it worked before, it should work again. Backtrack and find where you screwed up"
    Ok, the car was acting like the motor was getting juice, but not turning as I could feel the car jolt when put into gear. The wheels turn free when in drive. That got me thinking. The mg2 motor is getting energized but isn't turning. It acts like it can't turn or won't turn. It's a 3 phase motor so that means each coil gets energized in order 1,2,3 so it can pul the armature via magnetic force towards the next set of windings. Could it be that the wires to the windings are not in order?
    I go to the inverter and see the three cables attached U,W,V. Hmm I think if they should be in alphabetical order, they should be U,V,W. i pulled up a picture on the Internet and Bingo! Two wires reversed. What a stupid rookie mistake!!! I'm so glad I didn't overheat the windings and fry Mg2. Kudos to Eric the battery guy.
    So, ego badly bruised, I screwed up. God I hate it when I make a stupid mistake!

    Now the shifter problem, well the steering wheel lock plastic cams on the bottom of the steering column were jammed and not energizing the lock solenoid. Now the shifter locks and the button needs to be pushed to move into Drive. The key also turns and comes out.

    So, with a spare inverter, ignition key assembly, shifter assembly and shift control module in possession, no parts were needed to fix this car. Just help from you folks on the forum, brains and a little skill, the car lives once again. I can tell you that I know 100 times more about a Prius than I did 2 weeks ago. Now I'm comfortable working on my wife's. I will be looking for another to fix up and sell.

    To all who directed me, gave me advice, and things to check and think about, I am indebted to you. Would I go through this process again.....Absolutely. I live to fix things. It's who I am. Thank you to all. Until next time, blessings : )
     
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  5. DaneH5

    DaneH5 Member

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    So, do you still feel it is a poor design as mentioned earlier in your posts? (y)
     
  6. royfrontenac

    royfrontenac Member

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    Hi Jerry - Glad you got the car going.

    Roy from Canada
     
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  7. royfrontenac

    royfrontenac Member

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    This post was put in after Jerry solved the mystery and got the car running and driving OK.

    Hi Jerry- this is the point in time that you reversed the stator leads on the inverter (after finding poor connection problems).

    Could you tell us what you think was the original problem with the car and your solution to getting the car running again, when you have the time. (like in a mystery theatre how did you identify the killer)

    Roy from Canada
     
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  8. DaneH5

    DaneH5 Member

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    Sounded like the round plug not being secured correctly caused original problem.
     
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  9. Jerry G.

    Jerry G. Junior Member

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    Good Morning,
    So as to recap with the Reader's Digest version, I'll do my best to keep it brief, but not so to leave out pertinent info.

    Driving car, all of a sudden it dies. I drive 1/4 mile back to work on battery. Check 12vdc battery. Its full. Try to start car and get triangle of death. Pull code with the Mini Vci-P3125, subcode 345. You folks on this forum help direct me. Some say its a burned up Mg2. I silently cry inside. I deduce it is the inverter. Also Key will not come out of ignition. I order a salvaged good inverter and ignition key assembly thinking this will solve my problems. In the process of removing the current inverter, I found that the Mg1 connector was never secured to the inverter and just hanging, bolts were missing and connector had arc'd badly. Previous bad mechanic work done to it caused this. I reassembled inverter and burped coolant system. Took the HV battery out and did a full service on it. Re-installed it. Went to start the car and the engine started, was charging HV battery and no codes. Put it in park, just a slight jolt with no movement. Checked shifter position switch, steering wheel lock nice person'y and key lock mechanism. Found broken metal piece on steering wheel lock. Repaired it with JB weld and a very small hose clamp, along with lubing the plastic cams that activate the lock switch. Voila, steering wheel locks and key can be removed. Tried starting engine again, same results. Slept on it and Re-traced steps in my head. A sleepless night.

    Re-traced my work. Thought about basic electric motor theory and how they work. Inspected the inverter. Noticed the three HV wires to Mg2. Checked my connection to photos on the internet. I'm color blind, so apparently they are color coded white, blue and green. Blue and green are the same to me. Anyway, I checked the labels U, W, V. I though hmmm, should they be alphabetical (you never know with things these days). Ahaaah!! Two wires were reversed. Should be U, V, W! Rookie mistake! Reassembled everything, fired up the engine, put it in Drive, and today I drove it to work. No Problems.

    So, as far as the car, all human error, with the exception of broken components CAUSED by human error. As far as engineering, there are flaws in the Gen I that were resolved in the Gen II and III cars that made SIGNIFICANT improvements in operation and efficiency based on my studies. Overall, this is a good little car. Unless you have deep pockets for dealer or specialized Prius Hybrid service, you have to be open minded, willing to accept change in design and technology, and throw out a lot of previous car mechanic experience and understand electrical theory and electronics and have a above-average knowledge of mechanics and engineering to work on these. This is what helped me along with stubbornness, persistence, the ability to read schematics and have proper manuals and equipment to service these specialized vehicles. The Mini Vci was a priceless tool and absolutely necessary in diagnosis. Don't leave home without it!

    All I can say is thank you all for your assistance and sharing of knowledge. Without you, this would have been a tragic story. The mystery is solved and put to rest. Over and out : )
     
  10. ericbecky

    ericbecky Hybrid Battery Hero

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    Congrats.

    Great recap as well. Interesting how things look in hindsight, eh?

    Looking forward to hearing your ongoing adventures.
     
  11. ChapmanF

    ChapmanF Senior Member

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    Thanks for the great recap!

    If I remember my motor theory right, the basic effect of swapping any two wires to a three-phase motor is it spins the other direction. :) In your case, of course, you've got a three-phase motor with a position resolver on the shaft so the computer immediately sees it go the wrong direction, which its control algorithms don't handle. (It would be fun if the computer just said, hm, ok, V and W switched, huh? I'll go with that! Probably wouldn't even be hard to do.)

    -Chap
     
    #71 ChapmanF, Oct 23, 2014
    Last edited: Oct 23, 2014
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  12. Jerry G.

    Jerry G. Junior Member

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    You're exactly right Chap. Three phase motor with two stators reversed would result in the two fighting each other instead of "handing off" to each other. So, instead of 1,2,3 1,2,3 1,2,3 repeating to turn the armature, you have 1,3,2 1,3,2 1,3,2 going nowhere. Try dancing a waltz or cowboy shuffle 1,3,2! Your partner would kick you! The computer never threw a code because it saw 3 stators. But, it didn't know the order of them.

    So, on another note and the next mystery, I bought a new keyfob as I never got one with the car. Just 1 key no fob. I tried the standard entry into programming sequence 12 times with no luck of getting the door locks to click. I can't get into program mode. Any ideas anyone?? The red LED still flashing on the dash.
     
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  13. CARSFAN4

    CARSFAN4 Junior Member

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    Hi Roy, I bought a 2015 Prius C and sometimes the hybrid battery gets low when I dont drive my car several days in a row. Can you send me the website address where I can shop for a lower price battery charger? Text it to me at:213-361-0460, Thanks
     
  14. ChapmanF

    ChapmanF Senior Member

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    Ordinary three-phase motor behavior is simpler than that, because of the symmetries involved: Change 1,2,3 to 1,3,2 and then unroll it some: 1,3,2,1,3,2,1, 3,2,1, 3,2,1 ...

    In other words, any time you switch any two leads on a three-phase motor, you simply make it spin the other way.

    The added wrinkle in a Prius is that there's a rotation-sensing resolver on that motor, so the instant the car's computer decides to spin the motor one way, and sees the shaft move in the other direction, the computer is like, wth?