P1121 after bleeding. Heater core?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by N23papp, Mar 3, 2018.

  1. N23papp

    N23papp New Member

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    I am at a loss. I can't get rid of this code. I've blown through 3 3-way valves. I just got a new coolant pump and valve. Patiently bled the system, and to no avail. Blowing only cold air, and the only code is p1121.
     
  2. ChapmanF

    ChapmanF Senior Member

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    Are you referring to the repair manual? If not, that would be my suggestion.

    The (first) reason the manual is important is it tells you the actual "detection condition" on which a code gets set:

    p1121dc.png

    Now you know what you're looking for: some reason why the position sensor voltage isn't changing, or some reason why the outlet temperature reads hot right at the start of coolant recovery, or some reason why the outlet temperature reading doesn't change despite recovering hot coolant. (With Techstream, of course, you can watch those values as the car operates, and you can see which of those conditions you've got.)

    If you have a code and you don't go to the manual to look up the detection condition, you end up really just guessing based on the one-liner fortune cookie for the code, and that just plain doesn't tell you enough to begin thinking through what could be going on. Without the information you need to think it through, you end up just replacing parts three times, or making guesses, or both.

    Once you've looked in the manual, of course, you don't have to stop after finding the detection condition; you've also got ten pages of troubleshooting procedures there you can follow to pin down what's going on.

    -Chap
     
  3. Raytheeagle

    Raytheeagle Senior Member

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    Welcome to Prius Chat (y).

    Some questions:
    • How many miles on your Prius?
    • Is there any damage to the wiring around the valve?
    • What is the TImeline of the 3 valve replacements?
    • All right now, over a couple of months?
    • The coolant in the radiator is showing full when the cap is taken off?
    Keep us posted (y).
     
  4. ruggb

    ruggb Junior Member

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    anyone still watching this thread?
    I have similar issue, and I have seen an older thread of my exact issue, but know one is watching that one.
    I replaced valve 6 months ago. Then a P1121 came back. I refilled overflow tank (about 1 qt.). It went away for 30 days, now it is back. All tanks are full. My techstream is not working=firmware issue, I need to reload 1.4.1 and I don't have it. I have a new one on order. Any way to determine if it is something other than the valve without techstream, or do I need to wait == it will be 2-3 weeks. Then I have to figure out how to use it.
     
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