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Codes P1121, P0A93, and C2318

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by carbroombroom, Feb 1, 2024.

  1. carbroombroom

    carbroombroom New Member

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    Hi all! I just bought a 2005 Prius a few months ago for pretty cheap, and knowing it had some issues. It's had the P1121 since I bought it, but I've held off on doing anything about it, probably for too long. Today I took an hour and a half trip and about a mile out from my destination, the generic red car with a bang, ABS, and VSC lights turned on. I pulled over, shut off the system for a minute or two, and turned it back on. ABS and VSC lights were off but the RTOD and the bangcar still remained.

    I had an appointment at my destination so I figured I would let it sit for the duration of the appointment (about an hour) and come back out and see if it turned off on its own (the previous owner mentioned overheating issues during the summer and it's the nicest it's been in a while around here)

    Still seeing the warnings, I skimmed some articles here and saw that sometimes low coolant will spur the generic bangcar, so I topped it off, as I had the coolant control valve to fix P1121 and the coolant to put in but hadn't yet. After that didn't fix it, I went to AutoZone to have the codes read and they produced P1121, P0A93, and C2318. Is it reasonable to assume that P0A93 is directly caused by C2318? I haven't heard my hybrid battery fan kicking up (I didn't realize it existed until I read some articles in this forum, granted I play my music semi-loud so maybe I just missed it?)
     
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  2. carbroombroom

    carbroombroom New Member

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    After sitting overnight, the carbang has disappeared. Still plan on taking advice I get here. It's about 20 degrees cooler now than it was when everything got thrown initially. Check Engine from P1121 is still on. Anyone have any advice for checking the HV system fan for how loud it should be? While the car is running, I went ahead and turned off all climate and radio. I can hear nothing but the see-sawing from the coolant control valve.
     
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    Those codes are probably unrelated.

    P1121 is usually a bad coolant "3-way" control valve. (recommend a Toyota part)

    P0A93 is "the inverter got too hot". Commonly caused by a failed inverter coolant pump. Power the car to ready, then take the cap off the inverter coolant tank and see if there's movement.

    In cold weather the coolant can "swirl" around. On a hot day it's visibly "turbulent". If there's no movement then replace the pump (again, Toyota part is most reliable).

    C2318 sets when the "transmission control module" sees less than 9.3V at the B+ terminal for more than 1 second. This system only engages or releases the parking pawl to prevent the car from moving.

    Slight chance that a very weak 12V battery could set this. There's a particular B+ wire for the TCM in the underhood fuse box that can corrode. I'll have to check my notes later as to specifics.

    You might consider getting your own scantool. Here's a thread that reviews several apps and devices. Some are capable of scanning codes and data from all systems on a Gen2 Prius

    https://priuschat.com/index.php?posts/3290690
    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Feb 2, 2024
    Last edited: Feb 2, 2024
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  4. carbroombroom

    carbroombroom New Member

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    Thanks for your reply. I'll check that inverter coolant tank when I get home today, and while I'm under there I'll check the fusebox too.
     
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  5. carbroombroom

    carbroombroom New Member

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    It's been far more than that day, but I did check yesterday after these codes came on again and the coolant in the inverter's reservoir (the pressurized one, yes?) is stagnant. no movement. Guess that means I'll be buying an inverter coolant pump. I've been seeing Toyota part only, is that still the case?
     
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    It is in my book. I prefer not to have to do a job twice because a (cheap) part failed after a few months.

    Some others are OK with that.

    What's more important to you - time or money?

    Posted via the PriusChat mobile app.
     
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  7. carbroombroom

    carbroombroom New Member

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    So after watching some videos, I've noticed that other's inverter coolant reservoirs have PINK coolant in them, and I had assumed that the inverter would've used a different coolant that Toyota had made like, proprietary or something, because when I had looked at my reservoir the "coolant" inside was black and I'm unsure if it's even coolant at all. I'm not going to flush and replace until I have a new pump to make sure that I don't run the inverter dry, but this is really concerning
     
  8. ChapmanF

    ChapmanF Senior Member

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    Ewww.
     
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  9. carbroombroom

    carbroombroom New Member

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    I can hear the pump trying to operate (I think, behind the driver's side headlight?) but the hoses are empty and the reservoir is just stagnant with this black / brown liquid. I might flush it anyway considering the hoses are empty
     
  10. carbroombroom

    carbroombroom New Member

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    You're telling me!
     
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  11. carbroombroom

    carbroombroom New Member

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    I should mention that after watching these videos I now also know what the pump sounds like while it's running. I think it's running dry because I can hear a up-down-up-tink noise repeating whenever I start the car (I can post a video later). It's also strange to me that I only start seeing errors when I go > 20mi or so in recent Illinois weather (mid 60s - low 80s) or > 70 mi in mid 50s weather, considering that others have claimed that failed pumps give them trouble within 10 minutes of driving on the highway. I also never see the car go into limp mode like others have said, and the hybrid system appears to run normally (regen, drag, battery levels) when the errors start popping up
     
  12. dolj

    dolj Senior Member

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    I hope somebody didn't fill the inverter coolant reservoir with brake fluid, thinking the inverter coolant reservoir was the brake reservoir!
     
    #12 dolj, Apr 16, 2024
    Last edited: Apr 16, 2024
  13. ChapmanF

    ChapmanF Senior Member

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    Or with ... whatever. I don't even know where you go to buy black brake fluid.
     
  14. carbroombroom

    carbroombroom New Member

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    I'm currently waiting for my drain to finish, but I have found out the following things:
    It was blue coolant, not mystery black liquid as I thought. Yellow reservoir + Dark blue coolant = Brown.
    It was severely underfilled, probably around 2-2.5 qt. in a 3.9 qt capacity system.
    Probably unbled if the reservoir appeared full but was underfilled
     
  15. dolj

    dolj Senior Member

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    Obviously not bought black, contaminated brake fluid goes dark/black, but luckily it was not that.
    If you are draining from the drain plug on the transaxle sump, that should take no more than 5 minutes. If it is going considerably slower than that, you may have a blockage you need to deal with.

    The image below shows the coolant drain plug looking at the transaxle from front to back.

    Inverter Drain Plug Location.png
     
    #15 dolj, Apr 16, 2024
    Last edited: Apr 16, 2024
  16. carbroombroom

    carbroombroom New Member

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    The initial push took less than 3 minutes— drained about 2 qts of blue coolant in that time. I then flushed it with pink and I was waiting for the drip to stop to get it as empty as possible. I had about 2 gallons of coolant on hand so I had enough to spare to flush with. I was able to get about 2 qts back into the system before the pump wouldn't push any more through. I just ordered a replacement pump and hopefully that will be the end of this mess
     
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  17. carbroombroom

    carbroombroom New Member

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    Just finished my pump replacement, haven't cleared the codes yet but night and day difference in the coolant reservoir. It's so gratifying to hear a gentle hum instead of a screech from an empty pump when I turn the car off.