Question about the CHRS pump

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Subetha73, Feb 22, 2021.

  1. Subetha73

    Subetha73 Junior Member

    Joined:
    May 4, 2019
    6
    1
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    Location:
    Illinois
    Vehicle:
    2005 Prius
    Model:
    IV
    Hi!
    My 2005 had fading heat and occasionally threw the P1123 code, but it was eraseable with my OBD, then the heat stopped altogether and the code is solid.
    Thought it was the coolant control valve, so I replaced that. Actually got decent heat.. For a day.
    I bled air from the coolant loop, got a few bubbles, no heat, then tried to jump the CHRS pump relay to purge air from the thermos.
    No pump activity. No amps reading.
    Does this mean the CHRS pump is dead?
    I jumped it with the car off.
    Should I do the jump when I am in IG mode?
    Thanks for your help! :)
     
  2. mr_guy_mann

    mr_guy_mann Member

    Joined:
    Sep 3, 2020
    435
    186
    0
    Location:
    NJ-USA
    Vehicle:
    2006 Prius
    Model:
    Four
    So you have several things going on here. The CHS relay is fed by the 10A CHS W/P fuse which should supply battery power. So if you have no current flow when you jumper the relay (assuming that you jumped the correct terminals) then there is an open circuit somewhere. Could be the pump. Or the connector, wiring/ ground, blown or issing fuse, etc. (If you have a copy of techstream you should be able to command the pump or the coolant valve to operate from the engine ecu bidirectional tests menu).

    P1123 is the coolant control valve position circuit is high. The position sensor is a 3-wire potentiometer with a 5V reference, signal, and signal ground. A high voltage code could be a bad control valve or connector, or an open circuit for the signal ground (or possibly the signal circuit is open) or the signal circuit is shorted to 12V somwhere. You wou have to measure the circuits at the connector while it's plugged in to see what is going on.

    I assume if the coolant valve doesn't work then that could/ would affect heater function. But you could also have problems with the ICE coolant thermostat, the heater temperature blend door/ servo, the A/C (electric) water pump or its wiring, a clogged or airbound heater core, etc .

    Posted via the PriusChat mobile app.
     
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