2012 Prius Inverter Pump Code P314A Repairs

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by NotRecommend, Sep 14, 2023.

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  1. NotRecommend

    NotRecommend New Member

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    Hey there Prius owners! I need some help with a current issue with my car that I haven't seen any threads for. I want to preface this by saying this is my first Prius and I'm not a "car guy" by any means so some explanations may need to be very basic for me to follow.

    I own a 2012 Gen 3 Prius Two with 180,000 miles. While driving, it would briefly flash the red coolant temperature light for about 5 seconds then go away. It did this once and I took it to AutoZone to have OBD codes read as I didn't have a reader. No check engine light ever came on and the car didn't even beep when it flashed the light. Since there was no check engine light, their OBD2 readers came back empty and there were no codes. I thought it may be a fluke, but I decided to do my own research to try to find any answers. The only information I could find was to check fluid levels and that the water pump may be beginning to fail.

    The next week, the same thing happened with the flashing red light. This was a cause for concern so I took it to a local mechanic shop to have them diagnose and fix the problem. I got a call from them the next day and they said they got two codes and their codes led them to believe the water pump and auxiliary water pump (I assume auxiliary and inverter pump are the same?) needed to be replaced. They quoted me $1600 for the repairs and diagnostic. I took the information to do some of my own research and found out the pump failures are quite common around 150,000 miles and should be replaced to keep everything running smooth. I gave them the green light and they performed the repairs for me.

    While my vehicle was in the shop, I purchased a Bluetooth OBD2 reader and downloaded Dr Prius and Hybrid assistant on my phone. After getting my car back, I drove it completely fine the next day for a 1hr round trip to and from work. The next morning I decided to pull out the reader and check if there were any codes just to satisfy my curiosity. I checked for codes and the car went into "Check Hybrid System" mode and wouldn't let me drive. It was giving me codes P314A for battery code and P148F for engine code. This check hybrid system was new. I googled the codes and found the codes are for Inverter Coolant Pump Speed Signal and Coolant pump over revolution respectively. I assumed these were the two codes originally at the shop, but I am not sure as they did not tell me the codes they received. I could not drive it due to the check hybrid system mode.

    Later the same day I called the shop who did the repair and asked if they had forgotten to clear the codes and that's what I was seeing. He said they might have forgotten to since there was no check engine light and he recommended I clear the codes and see if they persist. He also told me they do not mess with the hybrid system and did not see the check hybrid system mode at all while it was in their possession. I cleared all codes and restarted the car and the P148F never came back, but the P314A did. After doing the same thing a few times, the car no longer said Check Hybrid system and the code didn't appear. I drove the car around the block and consistently checked for codes and neither one appeared. After finishing my drive I repeatedly turned the car on and off to make sure no codes came back and everything seemed fine.

    Fast forward about 30 minutes and I went out to check for codes again because I still had a sinking feeling. I plugged in the sensor and checked for codes. The infamous P314A code was back, but still no check hybrid system. I looked under the hood and there is no movement in the inverter coolant reservoir. It seems like something else is wrong even though the inverter pump has been replaced. Has anyone else experienced this issue and what do I need to do to fix it?

    TLDR: Code on OBD2 reads P314A. Inverter coolant reservoir does not seem to be moving fluid while the vehicle is turned on. Inverter pump replaced, but issue persists.
     
    #1 NotRecommend, Sep 14, 2023
  2. Tombukt2

    Tombukt2 Senior Member

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    If you put your hand on the pump and you feel it running then you need to do some further investigation usually you can hear it but some people that may not be the case generally if you put your hand on it you can feel it then with the reservoir cap off you could pinch the output hose of the pump and then let it go and see if you see movement in the tank sometimes the movement is very slight The water doesn't have much resistance against it through those 3/4-in hoses so it tends to flow pretty well but not really fast if it moves too fast the BTUs and the heat can't be removed from the coolant because it doesn't dwell long enough in the space that cools it the radiator the fan what have you so if it moves through there too quickly the heat doesn't get dissipated into the atmosphere it just stays in the coolant because it's moving so fast.
     
    #2 Tombukt2, Sep 15, 2023
  3. ChapmanF

    ChapmanF Senior Member

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    In Gen 2 the inverter cooling pump was just a simple 12 volt pump that would be on or off, and it would be on whenever the car was, which made it easy to test. Any time the car is IG ON, you should be able to go look for turbulence in the coolant.

    In Gen 3 it is a variable speed pump, controlled the same way as the one for the engine, so it's not running at the same speed all the time. It has a tachometer so the ECU can know how fast it is spinning, and it gives codes like P314A when it doesn't spin at the speed the ECU wants it to. Those codes have the same meanings as the P261x / P148F codes for the engine pump, other than being about a different pump.

    It sounds like your inverter cooling pump, even though replaced, isn't working right. Where was it obtained?

    It is possible (if less likely) for such a problem to be in wiring. There will be troubleshooting steps for the code in the repair manual. You might want to go straight to the source for that

    Toyota Service Information and Where To Find It | PriusChat

    and not waste your time with the 2012 PDF copy that floats around the web, 'cause it's missing those sections. (It does have the ones in the engine section for the P261x codes for the engine pump, so because the pumps are wired and controlled the same way, you could sort of follow those steps with adjustments in your head, but it's probably easier to just go where the manual isn't missing the sections you want.)

    You can also find some info about the control and tachometer circuits over here. That post is also about the engine cooling pump, but again, because the control and tachometer circuits for the inverter cooling pump work the same way, you can sort of borrow the information, and just move it to different wires and a different pump.
     
    #3 ChapmanF, Sep 15, 2023
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