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Jumping CHS Water Pump with multimeter

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Sean I., Jan 27, 2020.

  1. Sean I.

    Sean I. Junior Member

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    I'm trying to jump CHS water pump using my multimeter but it's not working. Here's a little background:

    This is my first Prius (2007 89K miles) and I've had it for 6 months.

    50 miles after purchase from private owner, I had P2601 code pop and replaced the CHS WP with a generic pump from Amazon. Code came back after 50 miles. I went to the dealer and they said pump seems to be running but there is not movement of coolant and recommended replacing the pump with genuine Toyota part.

    I ordered the part myself and replaced it myself. CEL didn't come back.

    2 weeks ago, a 1000 miles later, CEL comes and with P1116 code. According to the manual, there is either clog in the coolant system or CHS sensor is malfunctioning.

    I thought I might have introduced air bubbles into coolant system when I replaced the pump so I found youtube video on how to replace and bleed coolant. The guy in the video ran the pump manually using his multimeter in order to circulate the new coolant.

    I tried it on my car with my multimeter but nothing. I used the following setting and applied it to pin 3 and 5 of the relay socket, the horizontal pins:

    upload_2020-1-27_15-31-38.png

    What am I doing wrong? The pump does run when engine is running, however I feel like it's running rather weak, compared to the pump I saw in the guy's youtube video. So I'm also uploading my car running:



    I was going to check the sensor and replace and bleed the coolant at the same time, but I wanted to make sure I can run the pump with multimeter before I even start.

    Any help is appreciated.
     
    #1 Sean I., Jan 27, 2020
  2. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    CHS = Coolant Heat Storage I think?
     
    #2 Mendel Leisk, Jan 27, 2020
  3. Sean I.

    Sean I. Junior Member

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    #3 Sean I., Jan 27, 2020
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  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Pins 3 and 5 are the relay switched terminals and are correct. Use a paper clip to jump the terminals and see if the pump activates. If it does, and if you can't get the pump to run using the multimeter, then maybe the multimeter fuse which protects against excessive current has blown.
     
    #4 Patrick Wong, Jan 27, 2020
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  5. Sean I.

    Sean I. Junior Member

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    Patrick

    thank you for your reply.

    So I just bought another multimeter (it was cheaper than replacing the fuses) and gave it another try to jump the pump. Nothing.

    Then I tested the relay terminal for 20V DC setting. Multimeter showed 5.8V but slowing increasing. Other terminals showed steady 12.81V. So I think this is a problem. What would you suggest?
     
    #5 Sean I., Feb 3, 2020
  6. Priuslover09

    Priuslover09 Member

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    I don’t think you can jump a water pipe. I could be incorrect about this.
     
    #6 Priuslover09, Feb 3, 2020
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Connect the multimeter negative test lead to body ground, and the positive test lead to pin 3 of the CHS W/P relay socket. You should measure ~12.8V (assuming the 12V battery is fully charged.)

    If you do not, check the 10A CHS W/P fuse. Remove the fuse and measure voltage at the fuse socket. One pin should show ~12.8V and the other pin will show 0V since the fuse is not installed.
     
    #7 Patrick Wong, Feb 3, 2020
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  8. Sean I.

    Sean I. Junior Member

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    Patrick,

    I'm getting 0V on the relay socket... what's my next move? I'm thinking take the relay box off and fix the connection?

    Perhaps I can "hotwire" the pump and flush the coolant while doing it?
     
    #8 Sean I., Feb 14, 2020
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Your next move is to check the fuse and if it is good, see if you can measure 12V at one terminal of the fuse socket.
     
    #9 Patrick Wong, Feb 14, 2020
  10. Sean I.

    Sean I. Junior Member

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    Patrick,

    I thought I subscribed notifications for this post but I guess I didn't.

    After driving for 15 min, I checked the voltage on fuse terminal for CHS WP and it showed 12.54v. And I checked again on relay terminal and voila! It showed 12.5v!

    Wierd.

    I switched to 10A on multimeter and tried jumping the pump but nothing. Then I check the voltage again on relay terminal and now it shows 0v.

    Does the circuit shut off after certain time after engine shuts off?

    And just to be clear, jumping the CHS WP with multimeter is to be done with ignition off, and with the battery still connected, correct?

    Posted via the PriusChat mobile app.
     
    #10 Sean I., Feb 21, 2020
  11. edthefox5

    edthefox5 Senior Member

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    The CHS pump does not run constantly it cycles on at start up to send hot stored water to the engine so it reaches temp faster for emissions and then again to store hot water. This cycling of the water flow is controlled by the 3 way valve. The relay is controlled by the Engine Control Module.

    Whats with jumping it out with a dvm? Just use a short piece of small gauge wire and jump from 12B+ to the contact point on the relay socket.

    Jump out the socket connect Pin 3 to Pin 5. There is a diagram on the relay itself.

    Pin 3 is 12 volts from 10 amp CHS WP fuse. 12 volts is always there.
    Pin 5 is pump motor.
     
    #11 edthefox5, Feb 21, 2020
    Last edited: Feb 21, 2020
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  12. Patrick Wong

    Patrick Wong DIY Enthusiast

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    As Ed indicated, pin 3 should have 12VDC at ALL TIMES.

    A few years ago, another poster thought he would be clever by determining the current consumption of the pump motor, hence he measured current flow across the relay socket. However since that seems to be too much for some owners, you are right that it would be much easier to use a paper clip.
     
    #12 Patrick Wong, Feb 21, 2020
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