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Red triangle and strange code: P0A39

Discussion in 'Gen 2 Prius Main Forum' started by snakedriver, Jan 17, 2020.

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  1. snakedriver

    snakedriver Junior Member

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    Hello folks, I'm hoping to get some guidance or advice on my wife's 2009 Prius Gen II. For a while, it had an intermittent red triangle warning light, and then it finally stayed on. I immediately suspected the hybrid battery, but my neighbor has a Snap-on scanner and diagnosed a P0A39 code, which means "Generator Temperature Sensor Circuit High"

    It's my understanding that this means there is no continuity in the electric motor temperature sensor circuit, which could be caused by a loose or corroded connection. All the troubleshooting instructions I've read so far say that it may need a new transaxle, which sounds ridiculous for a temp sensor.

    Does anyone have any advice for checking connections? Which connectors could it be?

    thanks in advance.
     
    #1 snakedriver, Jan 17, 2020
  2. PriusCamper

    PriusCamper Senior Member

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    Never read about that one on here... Have you done a search to see if there are any discussions on here about it?
     
    #2 PriusCamper, Jan 17, 2020
  3. snakedriver

    snakedriver Junior Member

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    Priuscamper, Yes I have, and there is very little available. I'm open to the possibility that the Snap-on scanner isn't compatible with a Prius. So I ordered techstream and a cable from ebay. Hopefully that gives me a code that makes a little more sense.
     
    #3 snakedriver, Jan 17, 2020
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  4. SFO

    SFO Senior Member

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    #4 SFO, Jan 17, 2020
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  5. snakedriver

    snakedriver Junior Member

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    Thank you SFO! much appreciated.
     
    #5 snakedriver, Jan 17, 2020
  6. bisco

    bisco cookie crumbler

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    how many miles on her?
     
    #6 bisco, Jan 17, 2020
  7. snakedriver

    snakedriver Junior Member

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    Just around 150k. She's a good car, It's a real bummer that this is happening. My '05 with 199k is like a Timex watch.
     
    #7 snakedriver, Jan 17, 2020
  8. snakedriver

    snakedriver Junior Member

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    Hello folks, I have a few updates since I last posted. I've tried to get this thing fixed with not much luck. I confirmed with TechScan that the code is indeed P0A39, "Generator Temperature Sensor Circuit High".

    I replaced the inverter coolant pump.
    I replaced the Hybrid Control module under the dash with one from Ebay.
    I had to reset the immobilizer by shorting pins 4 and 13 on the OBDII port

    The red triangle and P0A39 code came back.
    I think I may be dealing with a bad connection from this temp sensor, but I don't know where it is.
    I read the instructions sent by SFO, but can't figure out where Motor Temperature sensor #2 is on the transaxle. Can anyone show me?

    I really don't want to have to replace the transaxle because of a bad temp sensor.
     
    #8 snakedriver, Jan 29, 2020
  9. PriusCamper

    PriusCamper Senior Member

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    It might be worth independently confirming that the temp is high by clearing the codes/disconnect 12v when engine is cold and driving it till light comes on and immediately be setup to drain the trans fluid and get it's temp, or even easier, stick a thermometer in the fill hole, your choice depending on when the fluid was last replaced. Then from that point you'll be able to decide if you want to see what's wrong with the temp sensor or if it's confirmed to be accurate?
     
    #9 PriusCamper, Jan 29, 2020
  10. snakedriver

    snakedriver Junior Member

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    The code pops within 2 minutes of driving. I'm thinking that's probably not enough time to get that hot.
     
    #10 snakedriver, Jan 29, 2020
  11. Priuslover09

    Priuslover09 Member

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    Did you take to Toyota?
     
    #11 Priuslover09, Jan 29, 2020
  12. snakedriver

    snakedriver Junior Member

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    No, I didn't take it to Toyota. Should I? I doubt the dealership wants to work on an 11 year old car.
     
    #12 snakedriver, Jan 29, 2020
  13. Priuslover09

    Priuslover09 Member

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    But it’s there job to fix cars and sell cars for costumers.
     
    #13 Priuslover09, Jan 29, 2020
  14. snakedriver

    snakedriver Junior Member

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    I'm kind of a DIY guy when it comes to my cars. If I can't figure it out, maybe I'll take it in. Then again, maybe I'll keep the battery and the 4 new tires and make an artificial reef out of it!
     
    #14 snakedriver, Jan 29, 2020
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  15. Priuslover09

    Priuslover09 Member

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    Ok
     
    #15 Priuslover09, Jan 29, 2020
  16. PriusCamper

    PriusCamper Senior Member

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    In that case, it'd be wise to figure out more about the location of the sensor and how direct of a reading it is from the stator. If there was a failing stator that was shorting out it could heat up in two minutes. But hopefully it's a just a faulty sensor, or the sensor is indicating a different problem?
     
    #16 PriusCamper, Jan 29, 2020
  17. SFO

    SFO Senior Member

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    Techstream should allow you to see the 'freeze frame' data from the time the DTC was logged.

    Did you have a chance to follow the steps 1 thru 6 of the workup for DTC P0A39 , if so what were the results?
     
    #17 SFO, Jan 29, 2020
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  18. snakedriver

    snakedriver Junior Member

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    SFO, I don't have the "hand-held tester" they refer to. Also I don't know where the "M10 motor temperature sensor No. 2 connector" is.

    Is it the one right in front of the transaxle, behind the radiator?
     
    #18 snakedriver, Jan 30, 2020
  19. dolj

    dolj Senior Member

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    You can just use Techstream (or another compatible scan tool) to look at the freeze frame data.
     
    #19 dolj, Jan 30, 2020
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  20. snakedriver

    snakedriver Junior Member

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    OK, I pulled the freeze frame data: upload_2020-1-31_16-10-6.png
     
    #20 snakedriver, Jan 31, 2020
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