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Was told my ECU (computer?) needs replacing in my 2007 after code p1121

Discussion in 'Gen 2 Prius Technical Discussion' started by zacthedrivein, Sep 2, 2018.

  1. zacthedrivein

    zacthedrivein Junior Member

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    took my prius in to the dealership after i got code p1121 which has to do with the 3 way valve for cooling. it was under warranty so they replaced it for free. as i leave the dealership, i make a stop at a store. upon turning my car back on, my check engine light comes back on. i take the car in and they have to do almost $600 in diagnostic to tell me they think they need to replace the ECU (computer?). i have no clue what im doing. not sure if this is under warranty, but i assume no. not sure what to do, any advice? do i just pay the $1650?
     
    #1 zacthedrivein, Sep 2, 2018
  2. zacthedrivein

    zacthedrivein Junior Member

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    i picked my car up from them today while i figure out what i want to do. here is what the paper said

    "code p1121 again. tried active test would not change values of valve. tried another valve, same result. tested wiring at valve found high resistance at ground. supplied another ground, still will not work. checked ohm readings from all the wires at valve to ECU and to ground. wires appear to be okay. called TAS (toyota auto service?) they said to check voltage at ECU pins 23-24 but did not know what if any voltage would show. had no voltage at pins. TAS suggest to try new ECU"
     
    #2 zacthedrivein, Sep 2, 2018
  3. edthefox5

    edthefox5 Senior Member

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    Never heard of ecu replacement because failure to cmmunicate with 3 way valve.

    It’s unlikely that just the 2 control legs of that ecu have failed.
    I see he never checked the 12 volts to that 3 way plug.

    Wonder if you have damage to the wiring? Lots and lots of posts on this site about mice eating the wires on a Prius. Take the cabin air filter out and see if there’s any evidence of mice damage. They like to build a little bed in there.
    Take the hatch Apart and take the spare tire out and look for rat droppings.

    What’s your diy skills. Own a voltmter?

    The engine ecu is behind the glove box.

    Connector on the 3 way:

    Pin 1. Yellow to pin 24 ecu
    Pin 2: Purple to pin 23 ecu
    Pin 4: Red B+ 12 volts
    Pin 5: Red to pin 20 ecu
    Pin 6: Brown is ground

    Take the glove box out the engine ecu is a silver can sits vertically behind it I think. Get the part number off it you can buy one on eBay cheap.
     
    #3 edthefox5, Sep 3, 2018
    Last edited: Sep 3, 2018
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  4. jerrymildred

    jerrymildred Senior Member

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    I second @edthefox5 on the mouse possibility.
     
    #4 jerrymildred, Sep 3, 2018
  5. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    And yeah, ECU is generally Engine Control Unit, and in Toyota's Repair Manuals: Electronic Control Unit. Why use a simple word like computer, when you can substitute a verbose three-word alternative, and then reduce it to an acronym.

    What does ECU stand for? - What Car?
     
    #5 Mendel Leisk, Sep 3, 2018
  6. JC91006

    JC91006 Senior Member

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    Maybe the tech crossed the hoses for the valve?

    Well it's under emissions warranty, let them figure it out
     
    #6 JC91006, Sep 3, 2018
  7. edthefox5

    edthefox5 Senior Member

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    yes we saw one guy here did that but there form fitted hoses so probably looks crazy. but probably....

    Upon further thought the reason the tech didn't see voltage on those pins is because the ecu pulls those pins low which is the other side of the coil. One side of coil has always 12 the other side is pulled low by the ecu. Pins 23 or 24 pulled low depending which valve you want to actuate. I think.....lol...
     
    #7 edthefox5, Sep 3, 2018
  8. ericbecky

    ericbecky Hybrid Battery Hero

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    Would be good to check the actual connector. Perhaps there is a problem with it?
     
    #8 ericbecky, Sep 3, 2018
  9. zacthedrivein

    zacthedrivein Junior Member

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    thank you very much for responding, i really appreciate. im not really a car person, so i have very little experience, but im decent with watching youtube videos and trying to figure stuff out, though im not super handy. i dont own a voltmeter. the people at my toyota dealership said my car is "drivable" but im not totally sure what that means in this context since we dont really know whats wrong with it. it seems to be driving okay, it just has the check engine light on. im currently unsure what to do (i will try to check for any signs of mice) because i dont feel that comfortable paying $1k for a fix they arent even sure about. especially after charging me $600 to "diagnose" a problem they didnt even really diagnose, technically.
     
    #9 zacthedrivein, Sep 5, 2018
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  10. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    If they ever figure out what the problem is, they should deduct all or most of that $600, that is not a trivial expense.
     
    #10 Mendel Leisk, Sep 5, 2018
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  11. bisco

    bisco cookie crumbler

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    how many miles on her?
     
    #11 bisco, Sep 5, 2018
  12. zacthedrivein

    zacthedrivein Junior Member

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    95,000 / 2007 5D hybrid. bought used maybe 4-5 years ago from a dealership
     
    #12 zacthedrivein, Sep 5, 2018
  13. edthefox5

    edthefox5 Senior Member

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    Wow those sobs hit you for $600?

    Sorry about that I don’t know where Salinas Ca is but is it anywhere near San Francisco they have the worlds best Prius repair center there called luscious garage.

    Wish you were closer that $600 would annoy me enough to go help you.

    It brings up something I always wanted to ask the forum in that wouldn’t it be easy to bypass the 3 way valve?
    There’s 3 hoses connected. One from heater core one from rad one from CHRS bottle. Couldn’t you just hook the rad and heater core hoses together bypassing the bottle. I realize the car would always throw a p1121.
    They don’t use the bottle in europe which means there is no 3 way valve.
     
    #13 edthefox5, Sep 5, 2018
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  14. zacthedrivein

    zacthedrivein Junior Member

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    the red ! triangle just came on today... really not sure what to do at this point
     
    #14 zacthedrivein, Sep 17, 2018
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  15. Raytheeagle

    Raytheeagle Senior Member

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    I’d get the codes read so you know where to start;).
     
    #15 Raytheeagle, Sep 17, 2018
  16. zacthedrivein

    zacthedrivein Junior Member

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    will the red triangle have its own code? because i already know the code for the check engine light, which i discussed in my original post. i wasnt sure if the red triangle warning thing would show up as a code or what. this hasnt happened before so i have no clue.
     
    #16 zacthedrivein, Sep 17, 2018
  17. Raytheeagle

    Raytheeagle Senior Member

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    It’ll have its own code and troubleshooting associated.
     
    #17 Raytheeagle, Sep 18, 2018
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