Misfire Codes After Engine Swap, Check Hybrid System

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Scott Dix, Mar 18, 2025.

  1. Scott Dix

    Scott Dix New Member

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    Location:
    Cedar Rapids, IA
    Vehicle:
    2010 Prius
    Model:
    ----USA----
    My 2010 Prius starting having some issues last fall. Here's a quick list of things that occurred in order (to the best of my recollection):

    - Head gasket failure, engine rattle. A tear down showed that the push rod in Cyl1 was bent.
    - Replacement JDM engine ordered.
    - 12v battery failed. It was only a few months old, but something was wrong. The car shutdown and lost power as I was pulling it into the garage. The 12v battery was replaced under warranty.
    - Check Hybrid System error appeared immediately after.
    - Engine swapped.
    - Can't start the car because of the Check Hybrid System issue.
    - Bought and installed a Maxx Volts Grid Charger and ran it for 20+ hours.
    - The following codes are being shown: P0A0D, P0300, P0301, P0302, P0304
    - I've tried clearing the codes with my standard reader, the Dr. Prius app, and disconnecting the 12v battery. They won't clear.

    I've used Dr. Prius to view the battery status (attached).

    At this point, I'm at a standstill. I'm wondering what my next step should be? I'm puzzled as to why the engine codes are there in the first place and why they won't clear. As for the Check Hybrid System, is there anything in the Dr. Prius output that is helpful? Could the 12v battery failure have damaged something?

    Any guidance on were to go from here would a hugely appreciated.
     

    Attached Files:

    #1 Scott Dix, Mar 18, 2025
  2. Scott Dix

    Scott Dix New Member

    Joined:
    Oct 20, 2024
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    Location:
    Cedar Rapids, IA
    Vehicle:
    2010 Prius
    Model:
    ----USA----
    Update. I'm an idiot and I didn't have the service plug properly seated. Good grief. Car started up, but runs rough. Probably need to drive it a bit.

    Mods, feel free to delete this thread.
     
    #2 Scott Dix, Mar 18, 2025
  3. MAX2

    MAX2 Senior Member

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    Third planet from the Sun
    Vehicle:
    2007 Prius
    Model:
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    Such errors are common, there is no point in deleting the topic. Someone will find it in the search and understand how to act.

    The error code P0A0D indicates an unlatched jumper in the battery as one of the reasons for the open control circuit.
    • When the power management control ECU detects that a safety device is operated, it will prohibit hybrid system operation or shut off the system main relay. There are four safety devices in three different locations. The first safety device is located at the service plug grip. The second one is located at the frame wire that is connected to the inverter with converter assembly. The third one is located at the inverter terminal cover where the motor and generator cables and No. 2 engine wire (air conditioning harness) are connected to the inverter with converter assembly. If the service plug grip, inverter terminal cover, or frame wire is removed, the interlock signal line will be open. If the vehicle is being driven, this condition will be determined to be an open circuit and the system main relays will not be shut off. If the safety devices are re-installed correctly, the system will return to normal when the power switch is turned on (IG).

     
    #3 MAX2, Mar 19, 2025
    Last edited: Mar 19, 2025
  4. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
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    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    I didn't see EGR cleaning (including intake manifold) in that laundry list. Did that get done?

    Also, what's the miles?
     
    #4 Mendel Leisk, Mar 19, 2025
    Scott Dix likes this.
  5. Scott Dix

    Scott Dix New Member

    Joined:
    Oct 20, 2024
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    Location:
    Cedar Rapids, IA
    Vehicle:
    2010 Prius
    Model:
    ----USA----
    The replacement engine only has 45,000 miles. I kept the EGR from the original engine and have it cleaned and ready to go. I plan to swap them every 25k or so to prevent issues with the replacement.

    I’ve been driving the car for two day and all seems to be well.
     
    #5 Scott Dix, Mar 20, 2025
    Mendel Leisk and ASRDogman like this.
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