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I have power to the engine water pump fuse, but not at relay

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by knix6, Aug 20, 2022.

  1. knix6

    knix6 2013 4, 7/19 2011 prius 2

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    I am trying to run down a P261C problem in my 2013 Prius, (not the 2011 that if you search my history, i reversed polarity and blew the big fuse in the bottom of the fuse box) I have the software, and it is indicating no rpms on pump at all. I have done the trouble shooting starting from the connector on the water pump (replaced water pump but didn't fix).
    I have power to the water pump 30 amp fuse, verified with multi meter to ground. BUT
    I have no power to the connection that the leg 3 of the relay. using multi meter to ground when car turned on, per the wiring diagram, I believe it is suppose to.

    What is between the fuse and the relay? do i have to pull apart the fuse box to get to the underside? or does the power travel from the fuse to the big white bar called relay integration that is not on the diagram?

    thanks in advance
    :) wiring diagram.jpg
     
  2. ChapmanF

    ChapmanF Senior Member

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    It's just a wire inside there, from the fuse terminal to the relay socket pole 3. Doesn't involve the integration relay at all.

    Hard for me to believe the wire has failed. You've confirmed voltage at the test points on both sides of the fuse, and you're checking pole 3 (the topmost pole) of the relay socket?
     
  3. knix6

    knix6 2013 4, 7/19 2011 prius 2

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    I was really hoping i could just plug in a new integration relay. I will confirm everything again, because i really don't want to pull that fuse box apart, i did it for my 2011 and it is really not fun. I think i had to take off fender/light wheel splash guard., sorry for whining, thanks for the help !! i appreciate it.
     
  4. knix6

    knix6 2013 4, 7/19 2011 prius 2

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    is there a way for me to "hotwire" an always on relay so i could see if power to the relay was my problem, like run a jumper from 12 volt source to the appropriate connection ?,, or is that asking for more problems
     
    Robert Watson likes this.
  5. Eddie25

    Eddie25 Active Member

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    What's the resistance between the fuse and the relay?
     
  6. Eddie25

    Eddie25 Active Member

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    Also, as obvious as it may seem, you need to answer ChapmanF's question on whether you are measuring both sides of the fuse.
     
  7. knix6

    knix6 2013 4, 7/19 2011 prius 2

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    sorry, Yes i did, both sides to the ground had between 12-13 volts. I will measure the resistance, great idea, first thing tomorrow, no i will do it right now
    between fuse (either side) and relay hole 3 there is plus 1 on the Ohm , between each side of the fuse 0 and with the leads touching it is 0.
     
    #7 knix6, Aug 21, 2022
    Last edited: Aug 21, 2022
  8. Eddie25

    Eddie25 Active Member

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    Huh, that's interesting, 1 ohm indicates the wire is OK. Have you double and triple checked voltage at relay pin 3? Are you measuring with the relay pulled? Might be helpful to post some pictures.
     
  9. Tombukt2

    Tombukt2 Senior Member

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    I had a problem with my factory original water pump and an aftermarket water pump after I changed my engine due to the blown head gasket in the crack in the center girdle part of the engine I'll have to go look at my notes and see what happened but basically my aftermarket pump that had been on the original engine working just fine when I put that all back in my car. I had a battery problem HV battery problem and I kept getting low RPM codes no water pump codes and something else. It's all here I'll have to go look at my stuff and see what exactly happened.
     
  10. knix6

    knix6 2013 4, 7/19 2011 prius 2

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    I was testing for continuity with the OHM meter, the multi meter i was using has one setting of 2000 of ohms, as I understand is anything below 1 means there is continuity in the wire, anything 1 or above means the wire is not connected, when i touch the multimeter leads together, it shows continuity because it is 0, when i touch the top of each of the fuses in the fuse box it shows 0 because they are not blown. If there is a simple wire on the right leg of the fuse that goes to the number 3 relay hole then it should be 0, not plus one.

    Man i am really confused if you are saying that one is an OK reading. but, I was testing for continuity, I will also look to see if i have a better OHM meter around that has more than one setting for OHM
    (also manual page is not the test i was doing, I just posted it to show part of why i was reading the ohm meter like that)
    yes i moved the leads around to make sure i had good connection, i had to take hand off to take photo. multimeter.jpg resist or not to resist.png [/QUOTE]
     
    #10 knix6, Aug 21, 2022
    Last edited: Aug 21, 2022
  11. Eddie25

    Eddie25 Active Member

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    Anything above 1 ohm doesn't mean the wire is not connected, and while true that a wire will typically read below 1 ohm, 1 ohm isn't really going to affect anything, especially not gonna cause a 12v voltage drop.

    The reading looks interesting to me because I've never seen a display like that with no decimals and no 'ohm' symbol, but it's been years since I've used a non-auto ranging meter and maybe it's just because it's a 2k ohm setting. Isn't the next click over on the meter a 200ohms setting?

    Taking a quick voltage reading between the two points (voltage drop) while you have 12v on the fuse might be worthwhile.

    What's the resistance measurement between pin 1 of relay and body ground (as per the test you posted)?
     
  12. rjparker

    rjparker Tu Humilde Sirviente

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    Reading on the 2000 ohm scale is likely to be wrong but the pic is too fuzzy to read the meter model to give you definitive guidance. If it is actually 1 and 0 ohms, the wire and fuse is fine. Better pics and the meter model would help.

    10 to 1 there is a simple mistake being made with your measurements. Points checked might be wrong, use of meter might be mistaken and or no actual probe connection is being made on certain tests. Almost the same odds on the wp itself being bad especially if it was aftermarket or original.

    What matters is the power and ground at the water pump AND the two digital signals / wires that control the water pump speed. To be precise you would measure the wp plus (1) and gnd (5) at the water pump, not using chassis ground. Among other things, the ground wire from the pump could be disconnected or open.

    There is no simple way with a low cost meter to check the digital lines, typically you want a graphing device such as an oscilloscope or one of the few graphing meters.

    97517303-06BE-4D23-99A3-E8155CF470E2.jpeg
     
  13. knix6

    knix6 2013 4, 7/19 2011 prius 2

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    SOLVED ---- I got a better multmeter that makes an audible sound. took out 30 amp fuse, to see if i could do fuse holder area to #3 of the relay. and after poking a bit got it to make the noise. so... why, check out the photo. the 7.5 amp fuse i pulled out to show the difference between what is going on in my fuseholder. (and it makes sense because I had to do quite a bit of testing on this car when i first got it with passenger front right damage as the water pump (phisically) damaged in the accident) my fuse box.png

    donor fuse box for 2011.png

    I do have to figure out how to fish it out of the depression, i wonder if i could get micro tweesers and pull it up?
     
  14. knix6

    knix6 2013 4, 7/19 2011 prius 2

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    and Thank you all for your time and help :)
     
  15. rjparker

    rjparker Tu Humilde Sirviente

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    You might be able to pull it up if the terminal is in one piece. Otherwise its pull the box apart or an external fuse holder bypass might be required.
     
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  16. Tombukt2

    Tombukt2 Senior Member

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    Just go with an external holder like Parker said if you get to picking around in that fuse box and mess something up and have to take it apart or if you got a real problem you might as well be looking the 2010 to 13 fuse box I guess the whole assembly once you start taking that bad boy apart it's pretty ugly
     
  17. ChapmanF

    ChapmanF Senior Member

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    The fuse box isn't really separately replaceable. Some of the lift-out units in it are, but the bulk of it is just part of the engine compartment wire harness—the wires grow right out of it, they don't all plug in. That harness is a pretty penny.