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Help to diagnose a P1116

Discussion in 'Gen 2 Prius Technical Discussion' started by ruggb, Jan 19, 2020.

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  1. ruggb

    ruggb Junior Member

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    This is the continuing saga of my Prius. I have gone thru a P1121 and replaced the valve for the 2nd time in 8 months. P1121 is gone. During the testing I got a P1116 because I lost more AF than I thought and the temp hit 240.
    Now everything is full. A few hundred miles later and I keep getting the P1116. Monitoring the temp with Torque app, it takes a long time to get up near 180. It varies between about 176 and 194, mostly about 183 after 5 miles. When I took it for a 10 mile tour and parked it, the radiator fill is cold. The big hose on drv side in front of and above the valve is warm as are other hoses in the vicinity.

    So why isn't the fill tube and that side of the radiator warm?
    What temp variation should I expect?
    What symptoms would a stuck thermostat give me?
    Is there a blockage? Where might it likely be if so?
     
    #1 ruggb, Jan 19, 2020
  2. dolj

    dolj Senior Member

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    P1116 points to a problem in the CHS coolant temperature sensor, usually stuck.

    MONITOR DESCRIPTION

    The coolant heat storage (CHS) tank outlet temperature sensor is used for monitoring coolant temperature in the vicinity of the outlet port of the heat storage tank of the CHS system. The resistance of the sensor increases when the CHS tank outlet temperature is low, and conversely, the resistance decreases when the temperature is high. The changes in resistance are reflected in the voltage that is output by the sensor. The ECM monitors the sensor voltage and uses this value to control the CHS system properly.

    If the sensor output voltage deviates from the normal operating range, the ECM determines that the CHS tank outlet temperature sensor circuit has malfunctioned, and sets a DTC.

    Examples:
    1. No changes occur in the CHS tank outlet temperature sensor signal (over 1°C [1.8°F]) after a predetermined length of time has elapsed from the start of the coolant recovering.
    2. A significant difference (over 25°C [45°F]) exists between the engine coolant temperature signal and the CHS tank outlet temperature sensor signal after a predetermined length of time has elapsed from the start of the coolant recovering.
     
    #2 dolj, Jan 20, 2020
    jerrymildred likes this.
  3. jerrymildred

    jerrymildred Senior Member

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    Good info, @dolj! I just replace my wife's CHSR temperature sensor a few weeks ago due to P1116 that only came up in chilly weather. It finally got chilly enough this morning to be fairly sure that I fixed it. Here's a good picture from @TMR-JWAP of the area involved. See post #9. I just made things worse | PriusChat

    It's super easy to replace, by the way, and you can get used sensors from wrecks if you want to be cheap like I was.
     
    #3 jerrymildred, Jan 20, 2020
  4. dolj

    dolj Senior Member

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    I can't really take any credit as it is straight out of the repair manual. But I thought it might help explain what was going on here.
     
    #4 dolj, Jan 20, 2020
    jerrymildred likes this.
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