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12v battery Drain P0A1D B2799

Discussion in 'Gen 2 Prius Technical Discussion' started by jaycoh, Jul 16, 2023.

  1. jaycoh

    jaycoh Junior Member

    Joined:
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    2008 Prius
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    Long time lurker… First time poster.
    Have searched, but haven’t found a solution to my issue.
    Went out to start in the morning and car was dead. Charged battery and everything was fine. Next day dead 12v battery again. So I went to Toyota and purchased a new OEM 12v battery. Swapped the batteries and then had a no start red triangle. Checked codes and got a P0A1D and B2799. I’m using a Bluetooth obd2 reader, so doesn’t give me the sub codes.I found a good used HV ecu and swapped it out. Did the 30 min relearn pin jump on the obd2 port. No luck. Same codes again.
    I did some parasitic drain testing on the 12v and realized I have a 2.7 amp draw coming from the HEV circuit. When I pull the fuse the amp draw is gone. I don’t think both HV ecus are bad so I’m wondering what could cause a parasitic drain on the 12v from the HEV fused circuit. All wiring and connectors look good and all other systems work. As of now the car will not go to not ready and the triangle and all lights are still on. I’ve disconnected the 12v many times to clear codes, but they just come right back. Any ideas of where to go from here? Could the HV relay on the big battery cause a drain on the 12v? All other fuses are new or checked good. Any help would be much appreciated.
     
    #1 jaycoh, Jul 16, 2023
  2. jaycoh

    jaycoh Junior Member

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    Gonna take the lid off the inverter and do some inspection.
     
    #2 jaycoh, Jul 16, 2023
  3. dolj

    dolj Senior Member

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    Unless the second HV Control ECU was brand new, I don't think you can conclude that with any certainty. What was the reason the second ECU was removed from the original car?

    Getting the sub-code would be helpful as there are in excess of 50 sub-codes, each one pointing to a specific failure in the ECU.

    It would be interesting to know if the 2.7 Amp draw goes away if you unplug the HV Control ECU.
     
    #3 dolj, Jul 17, 2023
    jaycoh likes this.
  4. jaycoh

    jaycoh Junior Member

    Joined:
    Dec 15, 2019
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    Vehicle:
    2008 Prius
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    Base
    The HV ecu was not new, but came from a running Prius. I will unplug it and see if my battery drain is still there. Thanks
     
    #4 jaycoh, Jul 17, 2023
    SFO likes this.
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