2008 Toyota Prius BaseFACTORY OEM SERVICE PROCEDURE

DTC P1121 Coolant Flow Control Valve Position Sensor Circuit Stuck: Description

Refer to DTC P1120Β  .

DTC TROUBLE DETECTION CONDITION CHART

DTC No. DTC Detection Condition Trouble Area
P1121
  • Water valve position sensor output voltage:

    No change despite the ECM sending a valve control signal or slow response

  • CHS tank outlet temperature sensor output:

    60Β°C (140Β°F) or more (when hot coolant recovering starts)

  • CHS tank outlet temperature sensor output:

    No change although the hot coolant is recovered

  • Water valve
  • Cooling system (clogging)
  • ECM
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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