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2009 Prius No Heat + P1121

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by cybertlc, Mar 24, 2014.

  1. cybertlc

    cybertlc New Member

    Joined:
    Mar 24, 2014
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    Location:
    Rochester, Minnesota
    Vehicle:
    2009 Prius
    Model:
    III
    Two weeks ago my CEL came on and the code was P1121. I checked the coolant level and everything seemed fine, so I figured I'd take it in soon.

    This week, my heater isn't working - it blows fine, but it is ice cold air. I again checked the coolant level and topped off the overflow, and nothing.

    Is the P1121 error related to the heating issue? Thoughts on this???
     
    #1 cybertlc, Mar 24, 2014
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Mar 8, 2008
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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    Check the coolant level in the radiator itself, not just the overflow reservoir. You need to remove the large black plastic panel over the radiator to access the radiator cap.

    DTC P1121 means that the engine coolant flow valve is stuck. That valve routes engine coolant between the cabin heater core and the coolant heat recovery canister. If the valve is stuck in the wrong position that would explain why the cabin heater is not working.
     
    #2 Patrick Wong, Mar 24, 2014
  3. jdenenberg

    jdenenberg EE Professor

    Joined:
    Nov 21, 2005
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    Location:
    Trumbull, CT
    Vehicle:
    2020 Prius
    Model:
    LE AWD-e
    When my coolant valve stuck, it was due to a low coolant level. The coolant acts as a lubricant for the valve. After a top-off of the coolant (it was low due to air bubbles left in when the coolant was drained/refilled), the valve loosened up. That was 155k miles ago and no further problems with the valve. I hope that you have the same experience,

    JeffD
     
    #3 jdenenberg, Mar 24, 2014
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