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P1121 - What is a Coolant Flow Control Valve Position Sensor?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by drive2much, Jul 30, 2012.

  1. drive2much

    drive2much Junior Member

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    The check engine light on my '05 Prius has gone on and off a couple of times and is giving me a P1121 code, which I found out means "Coolant Flow Control Valve Position Sensor Stuck". Does this have anything to do with the hybrid electric coolant pump that was replaced under recall a while back?
     
    #1 drive2much, Jul 30, 2012
  2. Ct. Ken V

    Ct. Ken V Active Member

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    drive2much,

    I believe not. I think it is in the engine coolant loop & has something to do with the hot coolant that is pumped into & out of the storage thermos tank. I'm not positive, but that's what I think.

    Ken (in Bolton,Ct)
     
    #2 Ct. Ken V, Jul 31, 2012
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  3. Britprius

    Britprius Senior Member

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    If the coolant is low due to an air lock finding it's way out this can cause the valve to stick, so check the coolant level and top up with SLLC if required. This may help.
     
    #3 Britprius, Jul 31, 2012
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  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    This has nothing to do with the pump replaced under recall.

    Check the engine coolant reservoir which is located behind the radiator. If the fluid level is low, then fill to the full mark and see if the CEL goes away after 3 starts. If the fluid level is good, then the coolant flow control valve needs to be replaced. This valve switches coolant flow between the coolant heat recovery canister and the cabin heater core, and is a fairly common North America Prius failure.
     
    #4 Patrick Wong, Jul 31, 2012
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  5. drive2much

    drive2much Junior Member

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    Ken, Britprius, and Patrick, Thank you all for your responses! I will check the engine coolant when I get home. Hopefully that will do the trick.
     
    #5 drive2much, Jul 31, 2012
  6. coopertino808

    coopertino808 New Member

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    drive2much, I have the same problem and just dropped my car off at the shop. Did topping off your coolant work?
     
    #6 coopertino808, Oct 24, 2012
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