Getting Negative HV Battery voltage readings

Discussion in 'Gen 2 Prius Main Forum' started by fullylaced1, Apr 25, 2020.

  1. fullylaced1

    fullylaced1 New Member

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    Hello, new to this forum. I have a 2005 Prius Gen2 (120,000) and have codes P0A80 and P3015. Thought about replacing the bad modules in the pack but wanted to read the voltage in the blocks with the Torque App. As I read the voltages, all blocks were -330 except block 1, which was 15.4. Does anyone know why it's getting that reading? does this mean all modules are bad?
    [​IMG]
     
  2. 05PreeUs

    05PreeUs Senior Member

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    Since block #1 reads mostly normal, I suspect that the wiring to the remaining blocks is messed up. This might be the simple result of a broken or badly corroded sensor wire connection in the HV pack. The voltage of each module depends on the connections before it, so break a link in the chain, and the chain gets shorter. In this case, you seem to have a single module chain.
     
  3. PriusCamper

    PriusCamper Senior Member

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    Voltage harness, aka Wire Frame #2 is likely your problem and it only costs $50 for a new one from Toyota... However Torque app sucks and that could actually be the problem. To be certain before you pull the pack to replace wire frame, try using Dr. Prius app... Also likely you have a bad module based on P3015 code, but one thing at a time.
     
  4. fullylaced1

    fullylaced1 New Member

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    Thank you for your insight! I took the battery pack out and it seems like all the bus bars have corrosion. I also checked the wiring harness and I’m not sure if this is normal? The pins looked fine, however.
    [​IMG] [​IMG]
     
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    I'm going to go with this being a Torque problem.

    The P0A80 and P3015 are pretty clear on their meaning, but having 13 blocks all reading a -330v is most likely a programming error on the app....
     
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  6. TMR-JWAP

    TMR-JWAP Senior Member

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    That is the plug end of wire frame #2. Good call for those who said damaged wires, because that is most likely a goner.

    The corrosion levels you see are very typical. You definitely want to take a look at the ecu pins.
     
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  7. PriusCamper

    PriusCamper Senior Member

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    The voltage sensing plug going into the ECU does indeed have healthy looking pins, but that black spot on the side of the plug is concerning. What does it look like in the socket? Perhaps pulling the ECU and taking it's cover off and looking inside will allow you to confirm it's nothing of concern?
     
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  8. Albert Barbuto

    Albert Barbuto Junior Member

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    The plug on Wire Frame #2 looks like it has seen some arcing. (circled)
     

    Attached Files:

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  9. PriusCamper

    PriusCamper Senior Member

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    Yeah, but he said the pins looked clean... But I agree, that black spot on outside of plug may indicate otherwise... I told him to look closer, so we'll see what he says.
     
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  10. 05PreeUs

    05PreeUs Senior Member

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    The arcing is not good, those energetic electrons went somewhere, likely into the HV control board :(

    By the looks of the modules, this pack has been apart before and I think more than once. AND, it appears one of them is leaking at the bottom :(
     
  11. ChapmanF

    ChapmanF Senior Member

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    Depends on what the meaning of 'normal' is.

    [​IMG]

    It is something we've heard of.

    Yours looks mild at this point. Some hit the jackpot:

    [​IMG]
     
  12. fullylaced1

    fullylaced1 New Member

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    I will look closer into the ECU and see what its like inside. Thank you everyone for your help!

    The pack was definitely took apart before and was done in poor fashion by the previous owner. The bottom frame holder under the modules is bent and the 28 bolts are missing. Is that another issue to worry about if the modules aren't bolted down? Also can i get those bolts cheaper at a hardware store?
     
    #12 fullylaced1, Apr 26, 2020
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  13. 05PreeUs

    05PreeUs Senior Member

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    HW Store bolts are fine, just make SURE they are the correct length.
     
  14. TMR-JWAP

    TMR-JWAP Senior Member

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    @fullylaced1

    If you're in no rush for these fasteners, PM me your shipping address and I'll send you a handful so you can do the job right. I have hundreds, if not thousands, of extras.

    If you'd like, I can also send a used OEM harness (that doesn't have arc damage). I'm sure I can find one that's in decent shape. May need corrosion cleaned off the bus bars though.
     
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  15. fullylaced1

    fullylaced1 New Member

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    Thank you, I found an oem harness from someone today, along with some bolts. I will take the old harness out tomorrow and see if it damaged the inside of the ecu as well. Thank you again!
     
  16. fullylaced1

    fullylaced1 New Member

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    So I took apart the battery ECU and found this on one of the pins. Is this a sign that the sensing harness is damaging the ecu? if so, would I have to re program a replacement ecu or would it just be plug & play?[​IMG] [​IMG]
     
  17. dolj

    dolj Senior Member

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    I don't think you could draw that conclusion. It is a known issue and one that no one has been able to explain, to date. Most people fix it by replacing the ECU with a good one, one where the plug has no corrosion (and obviously functions properly). It is possible to repair it when it is not too bad like yours. You just need to get a new plug and be good at board level repair.
    No, there is no programming required. Just swap them over and you are good to go.
     
  18. fotomoto

    fotomoto Senior Member

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    My guess is this another example of an "el cheapo" pack bought by the previous owner so A) they could fix the trouble lights and B) sell it. It's a common occurence.
     
  19. TMR-JWAP

    TMR-JWAP Senior Member

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    The level of corrosion on those pins isn't all that bad. There's a LOT worse out there that still work fine. I've got some photos from aa 2006 I recently purchased where the car had the P0A80, but was still running. It had 100x as much buildup as your photo. I was amazed. Purchase some electrical contact cleaner and some strong q-tips. I'd be willing to say you can probably get it cleaned up pretty well. I wouldn't put it in a battery I was selling to a customer, but I would be ok using it in one of my own batteries.
     
  20. TMR-JWAP

    TMR-JWAP Senior Member

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    For the non-believers.....the corrosion was bad enough that once it was all cleaned off, it had eaten away so much of the pin, that the pin fell off when I set the ecu on my workbench. Yet, the car only had a P0A80 and still ran ok.

    IMG_5972.JPG IMG_5973.JPG
     
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