P1116 / Overheating? Help fixing please

Discussion in 'Gen 2 Prius Main Forum' started by RockDaMan, Oct 17, 2020.

  1. RockDaMan

    RockDaMan New Member

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    Vehicle:
    2009 Prius
    Model:
    N/A
    Hi all. my weekend break got cut short when (see photo below)
    • first the master warning light came on (1)
    • followed by the check engine light (2).
    • Warning light intermittently would stay ion and go away.
      I parked checked oil (seemed fine) and continued my journey but 5 minutes later
    • warning light would come on and head unit showed text "Problem" and also
    • High Coolant Temperature Warning Light (3) came on.
    • Both master warning (1) and high coolant temp warning (3) would come on and go away again. Was driving 30Mph maybe. Check engine light (2) stays on all the time.
    I made a pit stop at a car parts store and bought Innova's RepairSolutions2 consisting of an OBD2 Bluetooth adapter and quite nice analyzer app.

    The app ran an analyses and showed: P1116
    Primary Fix: Replace coolant heat storage tank Temperature sensor. ($58.43)
    (see 2nd screenshot below)


    What do you all think?
    • Should I do follow the recommended fix and order a "coolant heat storage tank Temperature sensor" and see if I can replace it myself?
    • Take it to a car shop and ask them to replace the "coolant heat storage tank Temperature sensor"
    • Take it to a car shop and have them just "fix it"?
    • Something else?

    NOTE: I don't have a lot of experience working on cars at all, I do not have access to a workplace (unless you count the streets of downtown Brooklyn as workplace) but I am fairly hand, got a tech background and got a fair amount of tools.


    warning light.png

    RepairSolutions2 tool:

    RepairSol2.png needs_attention_screenshot.jpg
     
  2. mr_guy_mann

    mr_guy_mann Member

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    I would not replace parts based on a code that was pulled by an app that tells you what part to buy- hint, that app was designed to sell parts.
    It might end up needing a new temp sensor but I would do some testing to confirm this. The problem I see is you don't have a location to safely work on your car. Plus, the sensor is located at the bottom of the heat storage tank , which can keep a couple quarts of coolant at scalding hot temps for 3 days.

    Some thoughts about this: I would want to use a second app or scantool to make sure the code is accurate- sometimes I have have a scantool "lie" and give me incorrect codes or data. You would likely need a scantool/app that has Toyota specific coverage to read data for the heat tank temp sensor from the engine computer (most tools only have access to the limited "generic OBD2" data). On a fully warm engine I would expect all coolant sensors to read 180-210*F.

    Temperature sensors are 2 wire Negative Temperature Coefficient devices (NTC). They vary resistance inversely with temp- while pulling a 5volt reference circuit toward ground (0V). So at when very cold, resistance is high and Voltage is near 5V. as it heats up, resistance goes down and voltage decreases steadily towards 0V.

    If the code is correct, then something in the heat tank temp sensor circuit is not what the computer expects. If it is a high temp reading, then the voltage is low. How low? Could be a bad sensor, could be a short due to wiring damage or corrosion in a connector.

    replacing the sensor MIGHT fix it, but that would be a guess.

    Short form, I would recommend you take your car to a shop and have them diagnose this.
     
    SFO likes this.
  3. RockDaMan

    RockDaMan New Member

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    2009 Prius
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    Thanks. Really appreciate your help. I'll take it to the shop and bring the temp sensor replacement that I've already gotten in the meantime. Might save time and avoid them from having to order one in if they decide to needs replacement
     
  4. PriusCamper

    PriusCamper Senior Member

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    Most OBD2 readers have problems with accuracy for Prius... Dr. Prius app is designed specifically for Prius codes and subcodes and is essential to know what's wrong whenever a problem comes up. If you can get a refund on your existing code reader and buy one that's best for Dr. Prius you'll be better off in the long run: Hybrid battery diagnostic and repair tool for Toyota and Lexus
     
    SFO likes this.
  5. jerrymildred

    jerrymildred Senior Member

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    I've had a P1116 and replacing the sensor was an easy fix. However, it never overheated. It drove just fine, in fact. Are you sure you have enough coolant in the system? The over temperature alarm on your display combined with the sensor code, would send me right to the radiator.
     
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  6. mr_guy_mann

    mr_guy_mann Member

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    Question for you. I recently began using Dr Prius- what systems does the app cover? I know it can pull engine control module codes as well as battery ecu. ABS? anything else? Does it only get data for the battery ecu?
     
  7. PriusCamper

    PriusCamper Senior Member

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    It's not going to help you bleed your breaks or pull everything from every sensor, you need Toyota Techstream for that... But my understanding is it's going to pull the hybrid system subcodes and possibly other system subcodes, which most OBD2 readers can't pull... The app builder's philosophy is to create an app that will help you diagnose the most problems, while not directly competing with Toyota Techstream.
     
    Data Daedalus likes this.
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