P1121 Error Need Advice

Discussion in 'Gen 2 Prius Technical Discussion' started by Vysse, Jul 5, 2018.

  1. Vysse

    Vysse Junior Member

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    So I'm travelling in Dallas right now and I got the P1121 error code. First off is there anything stupid simple it might be. I'm reading that it could be low coolant? Second how much would it cost to replace the Coolant Flow Control Valve. Third do you think it's safe to drive back from Dallas to Arkansas (388 miles approximately) with this issue? I'm unsure if it's an AC/ heating issue or what.
     
  2. bisco

    bisco cookie crumbler

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    iirc, you can ignore that code until convenient. do some more googling, is that the 3 way valve?

    i would certainly check the coolant level 'in the radiator'.
     
  3. Al Bundy

    Al Bundy Member

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    prius takes a special coolant, if its low id hit a dealer i dont think most places carry it..
     
  4. JC91006

    JC91006 Senior Member

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    Drive it home and then take care of it. Emissions related, won't cause any harm
     
  5. Vysse

    Vysse Junior Member

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  6. JC91006

    JC91006 Senior Member

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    Low coolant doesn't cause that valve to fail, it seizes up because it's old. They fail at around the 8 to 10 year mark.

    If you insist on adding coolant to the radiator, add Toyota super long life coolant or an Asian car coolant that's pink.

    To access the radiator, you have to remove the black plastic cover on the front of your car. The radiator cap is under it. Only open the cap when the car is cool
     
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  7. Vysse

    Vysse Junior Member

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    Okay I'll take care of it when I get home thanks for the advice.
     
  8. andyg

    andyg Junior Member

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    JC91006,
    I started getting the code P1121 these last couple of days. I have a 2008 Prius with 192K miles. I first started getting the code about 6 weeks ago. Following Patrick Wong's detailed instructions in this forum, I changed the inverter water pump with an new OEM unit (Genuine Toyota (G9020-47031) Water Pump Assembly) that I ordered from Amazon. I also replaced the ICE water pump (with OEM new unit) at the same time and changed both ICE and inverter coolants. I used UView 55000 Airlift to refill the coolant and made sure there were no leaks or airlocks. I used Toyota's 50-50 coolant that I bought from my local Toyota dealer. The coolant levels are fine and I can see the inverter coolant swirling when the inverter is in operation. I have a ScanGuage II set to always monitor SOC and water temp and the water temp ranges normal between 182 and 188 degrees. I have not changed the engine coolant thermostat hoping it is working OK judging by my scanguage readings. I did order the thermostat along with the pumps but found it hard to remove the casing. I did not persist in removing as I was not confident that I could then put the new one in. I have driven about 300 miles since I replaced the pumps. Can you, Patrick or any of the experts in this forum advise me further on this problem? Thanks in advance.
     
  9. JC91006

    JC91006 Senior Member

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    P1121 means you have a bad 3 way coolant valve. That is located next to the inverter pump. Although it's next to each other, they are on separate coolant loops.

    If you recently replaced the coolant, just save the coolant that comes out and put it back in the car
     
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  10. andyg

    andyg Junior Member

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    Thanks, I wish I had the forethought to replace the valve too when I replaced the pumps. Being a first time DIYer it took me a day for each of the pumps.
    Which coolant should I drain out before taking out the detective valve - ICE, inverter or both?
     
  11. dolj

    dolj Senior Member

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    You may not have to drain off any, if you clamp off the hoses. But if you do have to drain coolant, the 3-way CCV is in the ICE loop and has no interaction with the inverter loop.
     
  12. andyg

    andyg Junior Member

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    Thanks. I will try clamping. But given how I struggled to get the clamps off and the on when changing the inverter coolant pump, I may resort to drain and refill if I am too cramped for room. My replacement valve will only arrive next week. I'll post how it goes.
     
  13. andyg

    andyg Junior Member

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    JC91006, dolj, and Patrick Wong,

    Thank you for your help. A couple of weeks ago I ordered Genuine Toyota 16670-21010 Water Valve Assembly Valve With Bracket from Amazon $85 and managed to install it. I have driven 1500 miles since without having to keep an eye on water temp. I also bought a set of hose clamp pliers on Amazon for $15 and would definitely recommend it to attempting this DIY. Even with these pliers it took me an entire day to slide the clamps off the two top hoses. Sliding the clamp off the bottom hose was no problem.Installing the new valve assembly was a breeze. UView 55000 Airlift coolant refiller was another great asset to use. With it, I could make sure there were no loose fitting air leaks when I connected the hoses back, and refilling coolant literally took a couple of minutes. I did not have any airlocks to worry about. I would like to change the engine coolant thermostat also given that I have 200k miles on the original. I found it a bit hard to access the two 10mm nuts holding the unit and gave up having struggled a lot to remove water valve hoses before. If anyone can post easy to follow instructions for it, I would appreciate much.

    Thanks again
     
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