Need help once again!

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Sergey K, Apr 6, 2025.

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  1. Sergey K

    Sergey K Member

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    Check engine light came on. Check hybrid system message lit up.

    2011 Toyota Prius Gen 3. 145,000 miles.

    Went to autozone and got 3 codes:

    P314A: INVERTER COOLANT PUMP SPEED SIGNAL

    C1241: LOW OR HIGH POWER SUPPLY VOLTAGE

    U0293: LOST COMMUNICATION WITH HYBRID VEHICLE/EV CONTROL SYSTEM

    Additional system status: Battery voltage 12.25V. Inspect battery terminals if they are clean and tight, including between terminal and the battery post.

    What can I do? The car starts and runs but only runs in gas engine mode.

    Any thoughts welcome!
     
    #1 Sergey K, Apr 6, 2025
  2. Tombukt2

    Tombukt2 Senior Member

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    And what are we scanning with What kind of scanner seems to me you have maybe more codes 12.2 in this group size of an AGM battery which is pretty much I think all you can get in this group size should actually be 12 3 to 12/7 voltage wise sitting at rest not with the car ready or any of that so you're about it point low but that should not cause any problems unless there's internal problems with the battery or something else I would get that looked that very quickly communication problems usually equal voltage to keep the can bus up or something along those lines If you can get a capable scanner and really read all of the codes you may have a few more.
     
    #2 Tombukt2, Apr 6, 2025
  3. ASRDogman

    ASRDogman Senior Member

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    You need a scanner that will read all the codes for the Prius.

    Seems your inverter coolant pump has gone bad.
    12v battery is low. How old is it?


     
    #3 ASRDogman, Apr 6, 2025
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  4. Sergey K

    Sergey K Member

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    The OBD2 reader I have is cheap and horrible so I went to get it scanned elsewhere. The scan was done by a local auto parts store called AutoZone. The printout they gave me says "FIX FINDER powered by Innova".

    The 12V battery is 2 years old.

    The 12.25V reading was in accessory mode with engine NOT running.

    I will check battery voltage with car off and with car running and post here later today.
     
    #4 Sergey K, Apr 6, 2025
    Last edited: Apr 6, 2025
  5. Sergey K

    Sergey K Member

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    Battery disconnected: 12.44V
    Battery connected nothing on: 12.39V
    With accesory mode (not started, only pressed power button twice): 12.04V
    Engine running: 14.65V

    Is this battery too low?
     
    #5 Sergey K, Apr 6, 2025
    Last edited: Apr 6, 2025
  6. Brian1954

    Brian1954 Senior Member

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    Your 12v battery should be good at the voltages that you listed.

    The P314A code should turn on the check engine light and also the master warning light (Read Triangle of Death). I am guessing that the scanner used at Auto Zone is not good enough to read all the codes that your car has. My guess is that you have an inverter problem or a cooling problem of the inverter.
     
    #6 Brian1954, Apr 6, 2025
    Last edited: Apr 6, 2025
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  7. ASRDogman

    ASRDogman Senior Member

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    You need to be more precise when you give reading. Many factors are involve if you want
    a good answer......
     
    #7 ASRDogman, Apr 6, 2025
  8. Sergey K

    Sergey K Member

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    So do you suggest I replace my inverter coolant pump? I just dont understand how a pump would cause the other codes such as lost comm with EV hybrid control system. It doesnt quite make sense.

    Any other suggestions besides pump replacement?
     
    #8 Sergey K, Apr 6, 2025
  9. Tombukt2

    Tombukt2 Senior Member

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    Wow that's not good for the Innova team usually well I thought their newer stuff would be able to certainly read the Prius I know my old 3200 series can even if it doesn't recognize the codes it puts the numbers up there and I have to look them up but at least it does that and it's early OBD2 .
     
    #9 Tombukt2, Apr 6, 2025
  10. MAX2

    MAX2 Senior Member

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    P314A: INVERTER COOLANT PUMP SPEED SIGNAL
    The inverter water pump assembly sends the water pump speed (measured value) signal to the power management control ECU. When the power switch is on (READY), if the water pump speed (measured value) remains too low, this DTC is stored.
    If the pump is not working, the inverter may overheat, so further operation is impossible.
    You need to check the voltage supply to the pump and its performance monitoring circuits.
    See the diagram.
     

    Attached Files:

    #10 MAX2, Apr 6, 2025
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  11. Tombukt2

    Tombukt2 Senior Member

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    It's a gen 3 so you get all the upgraded nonsense that goes on so yeah if you're inverter pump is fubar that's part of the hybrid system it won't allow the battery to charge it full speed when it gets warmed up because it's not cooling down because the pump is screwed up and so on and so forth so yeah kind of linked together funny how it works like that isn't it
     
    #11 Tombukt2, Apr 7, 2025
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  12. Sergey K

    Sergey K Member

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    MAX2, thank you for the electric diagram. I checked the IGCT relay and it was good. Then confirmed power coming to the 4 pin pump connector, isolating the problem to the pump itself.

    I then followed the video that PriusChat user NutsAboutBolts posted here to remove inverter to get to the coolant pump (I realized that you do NOT have to remove the large metal bracket under the inverter as you can twist the pump through the narrow opening at just the right angle and I hope this helps someone else):



    It was a pain mostly with the hard to reach screws, clips and connectors, but I eventually took the pump out (after about an hour) and ordered a new Aisin brand from Toyota. It will arrive tomorrow morning. I just hope that car still starts after assembly tomorrow since the entire inverter motor has to be removed to get to this coolant pump. This is a massive Toyota fail. Why would they put it in such an inaccessible spot??? Wish me luck for tomorrows re-assembly! I hope its not the ECU...
     
    #12 Sergey K, Apr 7, 2025
  13. Sergey K

    Sergey K Member

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    20250407_150422.jpg



    20250407_150701.jpg
     
    #13 Sergey K, Apr 7, 2025
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  14. Tombukt2

    Tombukt2 Senior Member

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    Yeah see the little pump I use will go up way by the reservoir and be in line with that hose coming out of the reservoir one inch of hose My Little pump the rest of the hose from the car and then wires running to the old plug which hopefully I've extended from using the standard female end and extend it at the time I remove that old pump and put it connector there a barbed connector and then put my pump way up there by the reservoir with the extended wires or if I can pick them up up there whatever it takes then this is never coming out again but you got to realize you're he's at 280,000 miles so hopefully with an original pump that will take him to his desired 560 or something I don't see it but whatever and this won't be done again on his watch or the car's life
     
    #14 Tombukt2, Apr 8, 2025
  15. Sergey K

    Sergey K Member

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    More Problems.

    So I installed a brand new Aisin inverter coolant pump. Put everything together and "bled" the new coolant by restarting the car a few times. Topped off at least 4 or 5 times to full line.

    Took the car for a test drive and got the triangle of death, check engine light and check hybrid system message within minutes of driving. :mad:

    I went back and squeezed all the coolant lines and verified the new pump is spinning by feeling it and I can feel the rotation vibration inside it.

    Checked codes again, its showing a new code along with all previous codes for 5 codes total:

    P0C73: Motor electronics coolant "A" control performance

    P0A93: Inverter "A" cooling system performance

    P314A: Inverter coolant pump speed signal

    C1241: Low or high power supply voltage

    U0293: Lost communication with hybrid vehicle/EV control system

    One other unusual thing I noticed is the 12V battery voltage reads unusually high at 14.91V with engine running. Also the radiator fans run full blast and car runs only on gas engine.

    Im totally lost. What else can I check or try? Is there a drive cycle that may clear it? Does it need certain time to verify pump? Or will I destroy my engine by driving around?
     
    #15 Sergey K, Apr 8, 2025
  16. Sergey K

    Sergey K Member

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    Ok good news.

    I fixed it but not sure how. :)

    I checked all fuses in engine compartment and all tested good but some fuses had corrosion and buildup on connectors ends. I replaced all fuses with brand new ones from a fuse set I bought.

    I also found a relay that I believe controls the inverter water pump (R7). I swapped relays with another relay thats for daytime running lights just in case. Swapped R7 and R6.

    I also checked all fuses under the steering wheel by gas/brake pedals. All checked out good.

    Started the car the inverter coolant in reservoir disappeared. From high to completely empty. I stopped car and refilled it and all issues went away and I can see the the coolant moving like crazy in reservoir now too where before I couldnt see it move.

    It was either corroded fuses, a bad relay or just a huge air bubble came out from the coolant hoses. Not sure what fixed the problem.

    Ill order and replaced both relays to new ones because they had some corrosion on connectors also.

    But for now, Im not getting any more chistmas lights on my dash and everything seems optimal!

    Thank you all for your help!

    Screenshot_20250408_213710_Firefox.jpg
     
    #16 Sergey K, Apr 9, 2025
    Last edited by a moderator: Apr 9, 2025
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  17. Sergey K

    Sergey K Member

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    Thank you to everyone for all your help! I love this site and I appreciate the help and suggestions by everyone here. Thank you!
     
    #17 Sergey K, Apr 9, 2025
  18. MAX2

    MAX2 Senior Member

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    C1241/41 If a malfunction is detected in the power supply circuit, the skid control ECU power source voltage drops, or there is insufficient voltage to operate ABS main relay, the skid control ECU will store these codes.

    These codes may be also be stored if the auxiliary battery voltage drops below 9.5 V.

    C1241/41 INF Code 553? - VM1 voltage is 16.6 V or more for 0.8 seconds.
    Trouble Area:
    • Improperly connected connector, deformation or corrosion of terminals

    • Auxiliary battery

    • Hybrid control system (Charging circuit)

    • Brake booster with master cylinder (Skid control ECU)
    Why it is high is not clear.
    Unadjusted multimeter? Parasitic interference?
    In any case, the condition of the auxiliary 12V battery is important for the operation of the car.
     
    #18 MAX2, Apr 9, 2025
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  19. ASRDogman

    ASRDogman Senior Member

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    Get some contact cleaner spray and spray the fuse box where the fuse/relay goes in
    and install/remove them a few times. That will help clean them out.



     
    #19 ASRDogman, Apr 9, 2025
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