(2005) random negative voltages on hybrid battery modules from OBD + P3030

Discussion in 'Gen 2 Prius Technical Discussion' started by NoTrueScotsman, Nov 7, 2021.

  1. NoTrueScotsman

    NoTrueScotsman New Member

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    So I didn't drive the car for a while and now it's throwing errors P3000 (high voltage battery fault) and P3030 (High voltage battery circuit monitor fault). So I checked with my OBD reader and the voltage readings are crazy, some are negative, and some are twice what they're meant to be (image at bottom of post)

    So we (me and a licensed electrician) tore the car apart and (very carefully) tested the modules with a voltmeter and they're all fine. So this possibly indicates something wrong with the wiring harness or ECU (which measures battery voltages) as opposed to the hybrid battery itself.

    I would take it to Toyota, but it's going to be very expensive to tow it there, and from everything I've read they won't replace the ECU or the wiring to it -- apparently they will only replace the whole battery, which would cost the same as the car is worth - making it pointless. Then I'm likely stuck with a car that needs to be towed *away* from Toyota at great expense, plus whatever they charge me to diagnose it.

    I've looked on the internet and can't find any relevant replacement parts for this car (I'm in Australia). I'd try replacing the battery voltage sensor wiring harness but simply can't find one to purchase and I'm not sure it'd work anyway.

    Any ideas of what I can do to get her going? Or is it going to be goodbye after 10 years of trusty service? Maybe my best option is simply to sell for scrap? I'm moving overseas soon so I need the car out of my hair but selling is obviously preferable to scrapping.


    [​IMG]
     
  2. Albert Barbuto

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    Check where the orange wiring harness plugs into the ecu. Corrosion on the pins is a common problem.
     
  3. dolj

    dolj Senior Member

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    You should be able to buy part no. 82165-47040 (Wire, Frame, No, 2) from your local Toyota parts dept. Should be in the region of AU$75 - AU$85. Alternately, you might be able to buy a good example from a wrecker for cheaper. Just make sure the orange connector is in pristine condition. If there is corrosion around pin 22 you might need to get a replacement battery ECU from the wrecker too.
     
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  4. glyndwr

    glyndwr Member

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    Also, ive had that issue myself 4 years ago.
    That time the battery ECU was faulty.
    The car has been standing for quite a few months, and today, the code P3030 returned.
    Removed the battery ECU, removed the covers from the ECU and noticed brown tarnishing of the pcb tracks from the battery connector to the individual chips on the pcb.
    Going to try to find a replacement battery ECU off ebay, last time i paid £35.

    They DONT need programming either, plug and play.

    Hoping the replacement ECU works this time, as last.
    Glyndwr.
     
  5. NoTrueScotsman

    NoTrueScotsman New Member

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    Thanks for the advice. You were right, that plug is absolutely fried.

    Anyone know if Toyota will sell me this part or do I need to go to a wrecker?
     
  6. dolj

    dolj Senior Member

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    That being the case, you will need a replacement ECU too as more than likely the corresponding pins on the ECU will be damaged beyond repair. As long as the replacement ECU pins are in pristine condition, buying a secondhand one from a wrecker is a good option.
    There is no reason to expect Toyota will not sell you the part, so go in, ask for a price and see what they say.

    The only reason to get one from a wrecker is that it should be considerably cheaper. You would also have to have a very good idea of what a good usable one looked like and it is not just what the plug looks like, you also need to inspect the battery end of the sense wires to make sure there is no corrosion and all the wires have solid continuity. You don't want to end up with a replacement that is worse than the one you have.
     
    #6 dolj, Nov 9, 2021
    Last edited: Nov 9, 2021
  7. glyndwr

    glyndwr Member

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    update on the new P3030 with my prius. This is the 2nd time in 4 years. The last time i changed the battery ECU.

    So, I kept the old original ECU.
    Tested and examinated it yesterday under an electronics light and magnifyer.
    What we found was 3 tracks on the pcb from the battery voltage connector to the chips on the board in a bad way and wth no continuity.
    The rest of the pcb looks very good.
    So, later, im going to solder in jumper wires and bypass the damaged tracks to see if i can revive the pcb.

    I`ll repot back next week.
    Anthony.
     
  8. glyndwr

    glyndwr Member

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    Update.
    I have fixed the battery voltage sensing ECU.
    It was a broken tracks issue on the pcb taking the battery voltage sensing signal from the plug to the chips on the pcb.
    In total, 3 tracks were open circuit, so I replaced the tracks with wire soldered to the relevant places on the pcs bypassing the damaged tracks.
    Successful and tested in the car, no error codes showing.
    The bad tracks were from R879 and R880 going to the IC pins 5 and 8,
    the other was pin 5 on lower pinset on the connector to R871.
    See pics before and after, to see if you could also repair your damaged tracks on the pcb in the future.
    I was overjoyed with myself that i managed to repair it to be honest.

    Glyndwr
     

    Attached Files:

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  9. TMR-JWAP

    TMR-JWAP Senior Member

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    Very well done!! Can't remember anyone having tried this previously. Glad to see another option available for DIY!
     
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  10. nancytheprius

    nancytheprius Member

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    awesome. how did you even manage to troubleshoot which tracks were broken? priuschat is very informational!
     
  11. glyndwr

    glyndwr Member

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    i could see the suspect track, so used a multimeter to test for continuity, looked at where the track started and finihed and tested that track line for continuity, notoved no continuity or join between the 2 points, therefore the track was broked at somepoint between the test points.
    checked all tracks in that area, and noticed 3 tracks were broken / severed, so jumpwer wired those tracks.

    Glyndwr.

     
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  12. Albert Barbuto

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    Congrats for the circuit board trace repair. Not many have the skill to do this. :)
     
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  13. NoTrueScotsman

    NoTrueScotsman New Member

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    Thanks very much for your help, I bought a second hand ECU and that fixed the problem. I've started a new thread as the car still won't go into ready, but I have all positive voltage readings now, and no error codes:

    2005 - No error codes but won't go ready - traction battery is low | PriusChat

    I did check with Toyota and the battery ECU part number isn't even listed in their system. Second hand off Ebay was my only option anywhere in Australia. Money wasn't the issue, but I'd read that Toyota won't sell you a battery ECU and it was correct.

    Thanks to everybody for your help in this thread, I wouldn't have been able to get as far as I've gotten without your help.
     
    #13 NoTrueScotsman, Dec 15, 2021
    Last edited by a moderator: Dec 15, 2021
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