Now.. P1636 - HV ECU Malfunction

Discussion in 'Generation 1 Prius Discussion' started by LEVE, Nov 6, 2017.

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  1. ChapmanF

    ChapmanF Senior Member

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    I've just been reading this thread, which I guess I missed when you first posted it, and I've got one burning question: why is so much of this thread about fussing with the Engine ECU behind the glove box??

    You gave the title "P1636 - HV ECU Malfunction", and that is the correct one-liner for the P1636 code. This is a code reported by your engine ECU about the HV ECU, so it already tells you two things: 1) the engine ECU is working well enough to report a code to you, and 2), as far as the engine ECU can tell, your HV ECU may be hosed. And considering the HV ECU is beneath the carpet in the passenger seat footwell, right where the flooding was, I can hardly think of any reason it wouldn't be right about that.

    Have you checked?

    -Chap
     
    #21 ChapmanF, Dec 12, 2017
  2. LEVE

    LEVE Member

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    Chap, you're correct, again. Yes, I have checked. I'm finding that the term "Engine ECU" is bantered about with little understanding. I've found that term describing the "HV ECU" beneath the carpet of the passenger side footwell, hence citing the Toyota Part Number.

    Unfortunaly my used parts supplier, Parts Market, sells the "Engine ECU" as the "HV ECU".. it gets quite confusing when talking to them. They subistuted an earlier Part# 98661-47051 for the one I requesed. Of course, it is not a direct replacement. I'll use that in a 2001 I have in the driveway that needs one, so it was no financial loss.

    Now I'm just looking for a good deal on the correct HV ECU Part# 8991-47061. Once I find one I'll install it and report back on this thread. I fully expect it to cure the problem.

    So, in this case, they've got me using the wrong parts nomenclature.
     
    #22 LEVE, Dec 28, 2017
  3. Brian in Tucson

    Brian in Tucson Active Member

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    #23 Brian in Tucson, Dec 28, 2017
    Last edited: Dec 28, 2017
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  4. LEVE

    LEVE Member

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    #24 LEVE, Dec 28, 2017
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  5. Brian in Tucson

    Brian in Tucson Active Member

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    It's on its way today!
     
    #25 Brian in Tucson, Dec 29, 2017
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  6. LEVE

    LEVE Member

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    I am just quivering with excitement to have the car back on the road. Thanks Brian, I appreciate your efforts.
     
    #26 LEVE, Dec 29, 2017
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  7. Brian in Tucson

    Brian in Tucson Active Member

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    Second one went out yesterday.
     
    #27 Brian in Tucson, Jan 7, 2018
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  8. dolj

    dolj Senior Member

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    My immediate thought is that these units are pretty reliable, so having a second one go on the fritz would get me to look at what is wrong outside of the ECU that is causing the ECU to fail.
     
    #28 dolj, Jan 7, 2018
  9. LEVE

    LEVE Member

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    I would agree, however, the two HV ECUs exhibit different symptoms. The second HV ECU was from a wrecking yard, so its history was unknown. It was DOA. The original HV ECU was seemingly intermittent.

    The replacement HV ECU would "brown out" the MFD. It was as if the replacement was drawing down the voltage needed to assure the MFD would work. I haven't tracked down the problem in that part, as yet, but it is intriguing. It, IMHO, without looking at the PCB, exhibits the symptoms of one, or more bad capacitors.

    Since Brian sent a second HV ECU on Saturday, I'm interested in seeing what this HV ECU will do when it's installed.

    In a couple of days, I'll know if I'm right.. or wrong. I hope that I'm right.
     
    #29 LEVE, Jan 7, 2018
  10. LEVE

    LEVE Member

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    Well, no joy with the second HV ECU. The three parts give three different symptoms. So, it's my opinion (and I'm willing to be corrected) that the HV ECU is part number specific. I'm sending Brian back the two parts and he's going to try it in his Prius. I'll know more then as well as ordering a used HV ECU with the proper Toyota Part Number.
     
    #30 LEVE, Jan 11, 2018
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