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My 114K mile Prius 2007 is ill - any thoughts...

Discussion in 'Gen 2 Prius Technical Discussion' started by DianneWhitmire, Apr 28, 2010.

  1. DianneWhitmire

    DianneWhitmire High PRIUStess

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    Some input?

    My 2007 Prius with 114K on it showed the check engine light last Sunday. I was off Sunday and Monday, and did not drive it those days after the light came on... I came back to work Tuesday morning IN my car, which drove fine. Service had it right away Tues morning. Late that afternoon, the tech said he couldn't get the car to show a code or ANYTHING -- and that the ECU was not talking to the computer. He wanted to keep it overnight and try it cold.
    Today, Weds, I am told the ECU has failed. The part at my cost is $383. The labor is $400.

    Now, the question: it's like being sick with no symptoms? My car drives OK. The only way I was aware there was a problem is the check engine light. That could be a symptom by definition, but if the car's running fine... weird?

    Any thoughts? Just wondering if there's a less costly alternative. Or, if this has happened to anyone else with a newer model Prius Gen 2 with high miles? I'm not upset -- I fully expected SOMETHING to happen eventually... just not right now! :rolleyes:

    Dianne
     
    #1 DianneWhitmire, Apr 28, 2010
  2. paprius4030

    paprius4030 My first Prius

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    Bad 12v. battery makes a Prius do weird things.
     
    #2 paprius4030, Apr 28, 2010
  3. DianneWhitmire

    DianneWhitmire High PRIUStess

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    Yeah, I checked, the ECU is very well protected and since the car won't even throw a code... it means it's bad. I think.
    Thank you for the thought.

     
    #3 DianneWhitmire, Apr 28, 2010
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Dianne,

    1. Which ECU are you talking about: the engine ECU? If so, I have not heard about your car's symptoms happening before.

    If you have no driveability symptoms other than the check engine light being on, then I question the diagnosis that the engine ECU has failed.

    2. Since your car is a 2007 and you log so many miles I would not think your 12V battery is bad since it has plenty of charging time. However some weird Prius electrical problems can be attributed to a bad battery or loose battery terminal connections.

    3. I'd suggest disconnecting the negative battery terminal connector where it bolts to the body for several minutes, then reconnect. The idea is to give all ECUs a fresh "reboot".

    If the engine ECU really needs to be replaced, you might consider buying a salvage unit, for example:
    http://motors.shop.ebay.com/__?_from=R40&_trksid=m39&_nkw=prius+engine+ECU&_sacat=

    Looks like the going price is $100-$200. This ECU is visible behind the glove compartment, however the instrument panel has to be disassembled before the ECU can be removed. My guess is that it might take 2-3 labor hours, including removing the passenger-side airbag located in the instrument panel.

    However, if you have no driveability symptoms then I would defer this ECU replacement for now. $800 is a lot to pay for a problem that does not impair the car's performance.
     
    #4 Patrick Wong, Apr 28, 2010
  5. richard schumacher

    richard schumacher shortbus driver

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    ?? I don't know what you mean by that comment in the context of a possibly bad 12V battery. A dying battery wouldn't damage an ECU, just make it act goofy.
     
    #5 richard schumacher, Apr 28, 2010
  6. dogfriend

    dogfriend Human - Animal Hybrid

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    Seconded.
     
    #6 dogfriend, Apr 29, 2010
  7. nahtanoj

    nahtanoj New Member

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    i had a BMW with a failed ECU and the car wouldn't run at all. i'm not familiar with the exact prius system, but i would think the car would not be operating normally with a dead ECU.
     
    #7 nahtanoj, Apr 29, 2010
  8. Bear68

    Bear68 Member

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    Going just with my aging, failing memory here, but I do seem to recall seeing in the manuals certain cases where engine ECUs show no codes but the MIL remains lit. The books generally shows if the light is on and no codes are found or no communication is possible, replace the computer.

    ******NOTE******* This is to be done ONLY AFTER verifying proper power, ground and good wiring to the DLC connector.
     
    #8 Bear68, May 3, 2010
  9. DianneWhitmire

    DianneWhitmire High PRIUStess

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    After several hours of diagnosis and my dash etc being removed and apart, my top Prius tech determined the ECU was bad, period.

    I would have thought that a bad ECU would mean a dead car but I am being told that a bad ECU can manifest itself in a few ways. One of them is when it quits "talking" to the rest of the sensors and computers, the check engine light comes on because it has a failure to communicate. (yes, I know the line, :rolleyes:)

    The Mother Ship, ie. Toyota bought me the new ECU and I paid for the labor. She's runnin' like a champ. Hope I get another 114K out of my green machine!

    Dianne

    PS: Patrick I was hoping you'd weigh in here. I still wonder what might have happened if I'd just let the check engine light remain on, and keep on going, but in the end, my common sense told me something HAD to be wrong, and I drive 58 miles each way to work. Reliability means the world to me with my late hours and commute.
     
    #9 DianneWhitmire, May 4, 2010
    1 person likes this.
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Dianne,

    Thanks for providing the resolution to this. Especially since you got a discount on the repair, it sounds like a very fair outcome. I agree that its important for you to have a reliable vehicle given your long commute.

    Do you know whether the tech tried disconnecting the 12V battery, to see if the engine ECU could benefit from a fresh start?

    A couple of years ago I had a driveability problem with my 2004 where the powertrain refused to provide more than a limited amount of power. The solution was to reflash the engine and hybrid vehicle ECUs. That appears to indicate that the memory in one of the ECUs had become corrupted.
     
    #10 Patrick Wong, May 4, 2010
  11. DianneWhitmire

    DianneWhitmire High PRIUStess

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    I brought your original post to the service director, and he conferred with the tech. I also just asked if they had indeed tried this. He said that they had to no avail which was why they conceded the part was necessary. It would have been good for Toyota had that avenue worked. In the case of my car, it was not a solution. Thanks though! :)

     
    #11 DianneWhitmire, May 4, 2010
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