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Hybrid ECU, Traction Batteries, or Bus Bar

Discussion in 'Generation 1 Prius Discussion' started by jds580s, Sep 2, 2011.

  1. jds580s

    jds580s Junior Member

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    Hi! I took my '01 Prius (118k mi) into the dealer for the EPS pinion shaft nut recall and to diagnose a intermittent problem with the check engine / red triangle coming on.

    It's not a consistent problem. But ever few days they have turned on. I've had the codes read a number of times and it's always the same p3000 and p3030 - nothing else to go along with them.

    No symptoms to speak of... Mileage is where I would expect for running the car with A/C in the hot summer.

    The tech at the dealership diagnosed it for a day then called to say they wanted to keep it overnight to run some more tests. The next day they called to say they reset the codes and couldn't recreate the problem and sent the car home with me. I asked what to do when the codes come back, and was told to bring it in then and the would take another look. 2 days later they were back on so they checked it out again and are now recommending I replace the Hybrid ECU. I inquired what they would change next if that didn't fix the problem and was told the Traction Batteries.

    I'm curious if their diagnosis sounds reasonable or if I should try simple things like replacing the Bus Bar hoping it's a fractured sensor wire with a bad connection that is throwing the code perhaps after getting jostled on the road.

    Any feedback is greatly appreciated!

    If it comes down to the batteries I'll probably go the Re-Involt route and install myself.
     
    #1 jds580s, Sep 2, 2011
  2. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    In my unprofessional opinion, if the ECU was bad, it would be bad all the time (or at least after it heats up). It sounds like a stab in the dark to me. It sounds to me like your inverter might be heating up (due to lack of proper cooling (ie: inverter cooling pump or change inverting cooling fluid)). It seems to me that a traction battery problem would give you more specific codes. I would check the inverter cooling pump first. I say all of this with a disclaimer that I am no professional but I am a DIYer with lots of experience. I would run this by Patrick Wong and Seilerts. Both of them seem to be very well versed in these areas.
     
    #2 usnavystgc, Sep 2, 2011
  3. jds580s

    jds580s Junior Member

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    Thanks usnavystgc.

    I hadn't considered the inverter or it's cooling pump yet. I appreciate the tip to check those out.
    My thoughts exactly on the ECU and Traction batteries. Almost all the the battery problems I've seen are accompanied by other codes, and the ECU seems like the thing that gets recommended for replacement but doesn't fix the issue most of the time.
     
    #3 jds580s, Sep 2, 2011
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I do not think it is likely that the hybrid vehicle ECU is bad. It is possible that a sense wire has broken and/or the traction battery ECU is bad, however.

    It would not hurt for you to open and physically inspect the traction battery and the sense wires. Good luck.
     
    #4 Patrick Wong, Sep 2, 2011
  5. seilerts

    seilerts Battery Curmudgeon

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    +1

    Further, let the car sit for two days, and check all module voltages with a volt/multimeter. Look for large differences, like a particular module or two that is more than 0.1V lower than the other 37.
     
    #5 seilerts, Sep 2, 2011
  6. tochatihu

    tochatihu Senior Member

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    Please do be cautious in opening and inspecting the battery box. The high voltage speaks for itself, any copper corrosion would have been caused by potassium hydroxide leaking from the cells. That chemical is bad for skin and especially so for eyes.

    Surely Patrick's comment does not imply that traction battery innards are harmless.
     
    #6 tochatihu, Sep 3, 2011
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Since the OP says that it is simple to replace the bus bar and that he is prepared to install a replacement traction battery, I assume that he is well aware of the safety issues involved. If not aware, then he would do well to download the relevant repair manual info from techinfo.toyota.com so that he does not end up injured or dead.
     
    #7 Patrick Wong, Sep 5, 2011
  8. jds580s

    jds580s Junior Member

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    Thanks all, especially for the notes on safety which are always worth posting.
    Over the weekend I went in to pick up the car from the dealership. Since they were not confident in their diagnosis they didn't charge for any shop time. Perhaps I wimped out because then I looked around the lot and ended up leaving with a newer 2nd Gen Prius.
     
    #8 jds580s, Sep 6, 2011
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