Prius 2nd gen: Triangle of death- first time owner

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by daevidz, Nov 9, 2019.

  1. daevidz

    daevidz New Member

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    Vehicle:
    2007 Prius
    Model:
    II
    i found website super useful in my time as a prius owner. I have also been converted into a fan. After owning my car i found some troubling things but overall it seemed to function alright. Now fast forward about half a year the triangle of death has appeared and im getting worried about having to replace the battery refurbing it. I pulled a P0A9C code and it says something about the battery temperature sensor. I looked online and on the forum for any fixes am still not sure of my options because im not sure if my situaton is the same as everyone else's.

    When the triangle first appeared i took it to my local mechanic and he pulled the code for me, asking for my options he wasn't sure since he didn't specialize in hybrids. I told him that the battery was charging and functioning properly, so he decided to clear the code for me and tole me that if it showed again I should go check it out. I proceeded to drive about 600+ miles on it afterwards and it was fine. But when i went to taipei and came back after a week the triangle reappeared. I drove it and the battery is still working and doesn't drain faster and it still charges fine too. So when does this mean for me?? Can i get away will just changing the sensor? or what other options do i have? Im located in Los Angeles, so anyone have any advise?
     
  2. dolj

    dolj Senior Member

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    You don't say whether you had the codes read again, but if you haven't, do that. You cannot just assume the P0A9C came back.

    If it is the P0A9C reappearing, here is some info about it:

    3 battery temperature sensors are located on the bottom of the HV battery assembly. The resistance of the thermistor, which is enclosed in each battery temperature sensor, changes in accordance with the changes in the temperature of the HV battery assembly. The lower the battery temperature, the higher the resistance of the thermistor. Conversely, the higher the temperature, the lower the resistance.

    The battery ECU uses the battery temperature sensors to detect the temperature of the HV battery assembly. Based on the results of this detection, the battery ECU controls the battery blower. (Thus, the blower fan starts when the HV battery temperature rises to a predetermined level.)

    DTC No. DTC Detection Condition Trouble Area
    1 P0A9C Battery temperature sensor malfunction
    • HV battery assembly (HV battery temperature sensor)
    • • Battery ECU


    HINT:
    After confirming DTC P0A9C, P0A9D and P0A9E, enter the following menus on the code reader live data: HV BATTERY / LIVE DATA LIST. Then, confirm the temperature of the HV battery by checking "BATT TEMP 1 to 3".

    Temperature Displayed Malfunction
    1 -45°C (-49°F) or less Open or +B short circuit
    2 95°C (203°F) or more GND short circuit

    I would also check the HV Battery cooling fan is clean and working.

    I hope that helps.
     
    #2 dolj, Nov 10, 2019
    Last edited: Nov 10, 2019
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    If we assume the code reader you are using is Prius friendly, the P0A9C is for temp sensor #1. Sensor #1 is at the non-ecu end of the battery pack, where the air ducting is connected. It's mounted to the bottom of the module on the passenger side of the battery. The bad part about this location is that I've seen them damaged quite frequently, as many people use that area for carrying/moving the battery around when handling them. Seems to happen most often by the $400 craigslist rebuilders. Other than having the RTOD staring at you, I don't think it will affect drivability of the car at all. The car recognizes that it's a sensor malfunction. Replacement of the sensor harness would require removal of the battery and almost complete disassembly. replacement of the #1 sensor by itself could probably be done without disassembly, but the battery would still need to be removed from the car and a replacement sensor spliced into the wires by reaching into the plenum area.

    Now, if the code reader you're using isn't prius friendly, who knows what the true code is....

    Many apps are available for android phones that will display the 3 HV battery temp readings. That would make it easy to see if one is acting weird.
     
  4. JC91006

    JC91006 Senior Member

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    How long have you had this car? Do you know if the HV battery has ever been repaired or replaced?

    If this battery has been "professionally" rebuilt in the Los Angeles area, then you're probably in for a nasty surprise when you open that thing up. I've seen so many professionally rebuilt batteries here that are a complete wreck, not sure I would recommend anyone to go that route in the Los Angeles area. The business seems to be all about profit and fast turnover, forget doing the job right..
     
    Raytheeagle likes this.
  5. daevidz

    daevidz New Member

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    Vehicle:
    2007 Prius
    Model:
    II
    just for anyone else who might come across any problems. I ended up clearing it myself. drove another 800 miles on it over 2 1/2 weeks and then the triangle came again finally. I read the codes, it was for P0A80 and P3011. at first i thought of reconditioning my battery by my self with this DIY video :
    . It is very well made, just that i was not to sure if i could handle a project like that at the moment. So research shops around LA (i live in LA) for battery reconditioning and found some place in el monte that seemed reliable from reviews on google and yelp. Went there asked some questions and paid $600 for two years or 30,000 mile warranty. Let's see how it goes. hope for the best and ill update on any problems so if people want to know.
     
    bisco likes this.
  6. bisco

    bisco cookie crumbler

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    might have been wise to ask here for recommendations, but i hope it works out for you!(y)
     
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