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Error code u029a-bad connection with skid control ecu

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by JesseR, Dec 24, 2015.

  1. JesseR

    JesseR Junior Member

    Joined:
    Dec 24, 2015
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    Location:
    Rhode Island
    Vehicle:
    2010 Prius
    Model:
    III
    So I got the yellow triangle and the check hybrid system warning this morning. Fortunately I had just bought a Bluetooth obd and installed torque on my phone (hadn't even taken the scanner out of the package yet) so I was able to read the codes. According to the Web, u029a is bad wiring or loose connection at the skid control ecu. That doesn't sound so bad compared to my first reaction when the warning lights popped.
    So after an hour of Internet research I can't find any info on how to get to and check the connections in question.
    Any help would be greatly appreciated since I need this car every day and there's no way I'm getting a shop to look at on Xmas eve
     
    #1 JesseR, Dec 24, 2015
  2. jdcollins5

    jdcollins5 Senior Member

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    Location:
    Wilmington, NC
    Vehicle:
    2010 Prius
    Model:
    III
    My DTC Chart for the 2010 lists U029A as loss of communication with the Hybrid Battery Pack Sensor Module. It lists the Power Management ECU and Battery Smart Unit as possible causes.

    Can you reset the DTC? I would try that first.

    The Battery Smart Unit is in the electronics compartment on the end of the Hybrid Battery case.

    Also, how old is your 12V battery? If this is marginal it can lead to random codes some time.
     
    #2 jdcollins5, Dec 24, 2015
  3. bisco

    bisco cookie crumbler

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    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    has any work been done to the car? how many miles? have you owned it since new?
     
    #3 bisco, Dec 24, 2015
  4. JesseR

    JesseR Junior Member

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    Rhode Island
    Vehicle:
    2010 Prius
    Model:
    III
    I've only had the car a little while but I have good records, it was serviced at a toyota dealership and other than oil changes every 5k there's not much there

    I reset the code and it just clears the lights on the dash but still runs in gas engine only mode. After sitting for a while it starts up without any codes and runs in normal hybrid mode for a few minutes before the codes pop and it runs in gas only mode again.
    It rained pretty heavy yesterday and Tuesday and its still been damp all day today.
     
    #4 JesseR, Dec 24, 2015
  5. JesseR

    JesseR Junior Member

    Joined:
    Dec 24, 2015
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    Location:
    Rhode Island
    Vehicle:
    2010 Prius
    Model:
    III
    Well, after clearing the codes and disconnecting the 12v battery for a few minutes, the problem went away and the car was problem-free for almost two years (except for it thinking a door was open every time it rained heavily).

    Fast forward to Thanksgiving day and the same thing is happening. The yellow triangle, the lost traction light, the check engine light, and the yellow exclamation point are all lit up. I've tried clearing the codes, before and after disconnecting the 12v battery, I've replaced the (4.5 year old) 12v battery with a brand new yellow-top Optimus battery and cleared the codes again. Nothing gets me more than about ten seconds of normal driving before all the yellow lights pop and I'm in gas only mode again. Damn.

    Is there anything else I can test or try to diagnose the problem before I take it in?

    Also, I only have torque-lite. Would the paid version be able to log more error codes that I might be missing with the free version?
     
    #5 JesseR, Nov 25, 2017
  6. Lev Dzhepko

    Lev Dzhepko New Member

    Joined:
    Feb 8, 2019
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    Location:
    Washington state
    Vehicle:
    2010 Prius
    Model:
    III
    Well, I didn't want to open a new post for the same problem.
    2010 Prius iii.
    I have the same error U029a - 123, which I could read with cheap techstream unit from Ebay.
    The history of the car:
    Unknown before summer of 2018. The car is from Arizona. Had 188000 miles when we purchased it.
    Then drove somewhat normally for another 14000 miles, cleaned EGR valve and pipe myself during that summer.
    There was some sort of an accident or accidents, because both front and rear bumper are painted, and left front wheel plastic shield is missing (I am not sure if this is correct name for that part).
    The problem with hybrid system came this fall, when the rainy season has started (coincidence?).
    The car displayed "Checked hybrid system" and several more lights and quit. Took it to toyota dealership, they advised replacing 12v battery, so we did replace it. I didn't help and their technician was able to find a "bad ground wire connection" somewhere.
    The car worked for about a month, and then during a long trip down to south Oregon it displayed all the warning lights and started to work in ICE-only mode. I was able to drive it back about 300 miles, but going uphill was painful without electric engine torque.
    Took it to dealer and spent considerable amount of money, they told me that my ECU needs to be replaced (1500$), I have purchased set of computers from salvage yard for 250$ and put it in, they reprogrammed it for another "1hour fee" and the car was drivable just fine for another 90 miles. Then it quit again.
    I've decided to purchase techstream reader from eBay and checked the codes, the one displayed was U029A-123 Lost communication with hybrid battery pack. I was able to reset all codes and the car was perfectly drive-able again for just several miles. Repeated this "reset" - "drive" cycle for a day or two and then the car stopped to work.
    I mean everything works, but I cannot clear this code anymore, it comes back 2 second after I reset it.
    Any suggestions? Where to look for a problem?
     
    #6 Lev Dzhepko, Feb 8, 2019
  7. Imrand

    Imrand Junior Member

    Joined:
    Dec 29, 2019
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    Location:
    Pakistan
    Vehicle:
    2011 Prius
    Model:
    V
    Hi there i have some problem i am getting U029A - Network as lost connection with hybrid pack...
    It appears in morning everyday and disappears in noon unable to understand as it started in extreme cold weather. Any suggestions. I have checked all connectors on hybrid battery pack side.
     
    #7 Imrand, Dec 29, 2019
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