Battery temp sensors activated

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by newonsh, Jan 11, 2025 at 5:11 PM.

  1. newonsh

    newonsh New Member

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    Hi all. I've been a long time Priuschat peruser who now needs some help. Hopefully some of you have had a similar issue and can point me in the right direction before flushing an absurd amount of dough at the Toyota dealer.

    I've had a 2012 Prius for 9 years and currently at about 290k kms. I bought it in 2015 with 50k and it's been close to bulletproof. I had to replace the heat pump several years ago and that's the most major issue till Fall 2024. It started leaking coolant, which I thought was the head gasket. It sat for about a month, which also killed the 12v (original). I replaced the 12v and, after further investigation, replaced the water pump and thermostat, which seemingly fixed that issue (no more P148F code, no losing coolant).

    The very next day (early Dec) I went to drive it and had P0A9E Hybrid Battery Temp Sensor A High, P0AC8 Hybrid Battery Temp Sensor B High, and P0ACD Hybrid Battery Temp Sensor C High all come on and went into limp home mode. The last battery health test I did with Dr Prius back in the summer said the battery was about 68% healthy. And I had Toyota test it a year ago and it tested healthy.

    Side note and perhaps related is the fact that I've had a rodent, I think a rat, in the vehicle off an on for the last couple years and actually spotted it running up the back seat the day the codes came on and found fresh feces in the spare tire well and by the 12v.

    Any advice or suggestions would be very greatly appreciated. Thank you.
     

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  2. Brian1954

    Brian1954 Senior Member

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    If you feel comfortable working around the hybrid vehicle battery, take out the orange safety plug and remove the covers on the battery and check the wiring for the three temperature sensors. If you are not comfortable working around the hybrid battery, take the car to a hybrid specialist or the dealership.
     
    #2 Brian1954, Jan 11, 2025 at 7:17 PM
    Last edited: Jan 11, 2025 at 7:29 PM
    Prodigyplace likes this.
  3. newonsh

    newonsh New Member

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    Thanks for the reply. I don't mind getting close to the battery. I planned to try that and have a look. It's the middle of winter here in eastern Canada and has been really cold. Looks like some milder days coming so I'll give it a go. I've inspected the high voltage and other wiring coming out of the battery compartment and around the 12v and battery fan but can't see anything obviously damaged. Next step will be to get the cover off and have a closer look.

    I'm no Sherlock Holmes, but having all three sensors tripped at the same time having no issues prior in 9 years, and seeing a live rodent scurrying around the trunk area leads me to believe it's a wiring issue of some kind.
     
  4. PriusCamper

    PriusCamper Senior Member

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    I'd like to think there's no way a rodent could access those wires as they're fairly well covered up. But we can be fairly certain that your symptoms are not because your hybrid battery has gone bad. All signs point to the temp sensing plugs and wires having something happened to them that's causing them to malfunction.
     
  5. PriusCamper

    PriusCamper Senior Member

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    PS: In looking at your error codes again, I'm a bit suspicious about the device you're using to read the error codes. It might be that you do not have the correct error code library for Prius in this device/app. Try checking the error codes with a different app or Toyota Techstream on an old laptop.