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ABS Relay 1 problem - brake accu?

Discussion in 'Gen 2 Prius Technical Discussion' started by Michciu94, Sep 17, 2022.

  1. Michciu94

    Michciu94 Junior Member

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    I’ve disconnect the resistor and multimeter say - 0,00-0,02 in diode test.

    But another strange thing happen - with resistor disconnected, the Relay 2 is working when I’m driving and I don’t have continuous beep now. When I brake I hear every 2-4 stop the motor working for 2 seconds - earlier the motor doesn’t on.
     
    #21 Michciu94, Sep 19, 2022
    Last edited: Sep 19, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    I am not sure why you are using the diode test position on your meter ... that's a specialized setting to show you the voltage drop across a semiconductor junction.

    Are you saying that, previously, commanding relay 2 on did not run the pump?
     
  3. Michciu94

    Michciu94 Junior Member

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    Previously Relay 2 run pump when I used Techstream and option to turn on that relay. Now with resistor disconnected it is turning on also when I’m driving. I’ve looks at graph and now Relay 2 is running when accu volt drops to about 3,2V.

    I also checked resistance with multimeter at option 200, a value was about 0,01-0,02 - i think it should show 0,2OHM?
     
  4. ChapmanF

    ChapmanF Senior Member

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    Is the 280 Ω shown in post #20 the resistance from pin 3 to pin 3 of the two relay sockets, with the resistor in place?

    That does seem too high.

    Does it show as open circuit (offscale resistance) when the resistor is unplugged?

    Then, with the resistor unplugged, what is the resistance from relay 1 pin 3, to pin 2 (the black wire) of the resistor connector?

    What is the resistance from relay 2 pin 3, to pin 1 (the white wire) of the resistor connector?
     
  5. Michciu94

    Michciu94 Junior Member

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    1. Yes, 280ohm when resistor in place
    2. I’ve checked resistor and now it shows 0,5Ohm
    3. When resistor unplug there is no connection between pins 3
    4. The wire that are going to resistor socket are green and pink
    5. From PIN3 of Relay 2 to wire green there is just 0,00 so there is connection
    6 From PIN3 of Relay 1 to wire pink I saw high resistance about 1500ohm.

    I don’t know if I measured it right becouse there is so tiny space and I’m alone.

    So as I think there is a problem at brake acculator?
     
    #25 Michciu94, Sep 19, 2022
    Last edited: Sep 19, 2022
  6. ChapmanF

    ChapmanF Senior Member

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    The wire colors you are reporting between IP1 and B19 are different from the black and white colors shown in the diagram you posted in #17.

    Perhaps that is a diagram for the US market or a different model year, and green and pink were used in your area for 2005.

    In any case, if you show 0,00 Ω from relay 2 pin 3 to one of those wires, I would lean toward calling the actuator ok. The high resistance between relay 1 pin 3 and the other wire there is what I would want to investigate further.
     
  7. Michciu94

    Michciu94 Junior Member

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    I think diagram is good resistor have 2 black wires with a socket and those socket are green a pink like on a schema.

    At 28 september im sheduled to mechanic, and then we will take off wipers and check connections near pump and everything will be clear I think - just measure from sockets to BM1 and BM2 and there will be clear if that is a pump problem.

    I think BM1 and BM2 connection at assy can be broken.
     
    #27 Michciu94, Sep 19, 2022
    Last edited: Sep 19, 2022
  8. ChapmanF

    ChapmanF Senior Member

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    What the diagram is literally showing is that the green and pink wires go as far as a blue connector IP1, where they change to black and white, and proceed to the resistor connector B19.

    B19.png

    Perhaps you are saying that your resistor does not have a B19 connector, but its wires are directly attached, and have the blue IP1 connector at the end? That would be a slight design change from what the diagram is showing.

    Something also is odd about your measurements in #25. You show 0,00 Ω from relay 2 pin 3 to the green wire. From relay 2 pin 3, I can only understand continuity via BM2, to BM1 internally within the actuator, and to the pink wire at IP1. I do not understand continuity from relay 2 pin 3 to the green wire.

    Likewise, I don't understand continuity (or even 1500 Ω) from relay 1 pin 3 to the pink wire. I would understand it to the green wire (but it would be much too high, and need to be investigated).

    Is there any chance your description in #25 had relay 1 and relay 2 swapped?
     
  9. Michciu94

    Michciu94 Junior Member

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    I’ve maybe mistake pink-green colours becouse there is so tiny space and I barely see what I measure. At one Relay and one pin was 0,00 and at another Relay some high resistance.

    i bet wrong BM1 to BM2 connect in actuator. What you think?
     
  10. ChapmanF

    ChapmanF Senior Member

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    That's what I would bet IF you had the green and pink colors reversed in post #25.

    So it might be worthwhile to confirm that's what happened, before making expensive bets.
     
  11. Michciu94

    Michciu94 Junior Member

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    Yes. I will confirm it 28 September with my mechanic - I will remove windwiper to have a access to brake acculator socket and then make measurement - if brake actuator motor will be bad then we will change it to used one.

    Is a 0.1V drop overnight at accumulator sensor normal?

    Is there any way to check used brake assy before mount? We can check resistance and motor but to check if it hold pressure we need to mount right? It is a little bit lottery with used part :(
     
  12. Michciu94

    Michciu94 Junior Member

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    Ive got used part and BM1-BM2 is 1,4Ohm, BMs to Ground are ok, but BM1 and 2 to MTT is about 500ohm, and the diagram said it should be 10Ohm but I see at the forum that it is normal value sometimes?
     
  13. Michciu94

    Michciu94 Junior Member

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    I have a question - can’t I just jump pin 3 relay 1 with pin 3 relay 2? The pump will run more noisy becouse no resistor but it will destroy something? The Relay 1 and Relay 2 don’t switch on together I think ?
     
  14. ChapmanF

    ChapmanF Senior Member

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    I don't know anything about whether the relays ever come on simultaneously.

    I guess if you have concluded that the open circuit is between BM1 and BM2 inside the actuator assembly, so that otherwise you'd have to replace the actuator assembly, you could think "what's the worst that can happen if I bridge these two circuits? Will I have to replace the actuator assembly?"

    I haven't checked the details here in the diagram or the available trouble codes, but one thing you could run into would be the ECU monitoring the relay outputs to confirm proper relay operation. I know Gen 1 took that kind of monitoring pretty seriously.
     
  15. Michciu94

    Michciu94 Junior Member

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    I think ECU make a Relays working just fine. I’ve checked it via active test tab and also monitor what ECU made when driving - ECU turns on relay 1 but nothing happen and then when pressure is low turns on relay 2 and pressure rising.

    Day after tomorrow I go to service so everything fill be clear.

    I think I can connect those pins but I don’t wanna risk.

    I have another question - what make that 0,2 Ohm resistor? It decrease amperage or voltage? Relay 1 have 25Amp fuse and Relay 2 30Amp so I think it decrease amperage? This resistor is very big and have huge radiator.
     
  16. ChapmanF

    ChapmanF Senior Member

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    Yes. :)

    The voltage across the (resistor and motor) in series will be unchanged, so the voltage across only the motor will be less, and the difference will be the voltage drop across the resistor, equal to 0.2Ω times the flowing current.

    The flowing current will be the same everywhere in the series circuit: the same in the resistor as in the motor. It will be whatever current the motor draws at the reduced voltage across it, and will equal the resistor voltage drop divided by 0.2Ω.

    So it is a chicken/egg question to say whether the resistor decreases the voltage or the amperage "first", but both will be decreased, and by such amounts that the equations work out.

    Suppose 20 amps end up flowing (so that the 25 amp fuse would represent a 25% safety margin). Then the voltage drop across that resistor would be 4 volts (20 A times 0.2 Ω) and the heat produced would be 80 watts (20 A times 4 V). That requires a large heat sink.

    In fact, a typical 80 watt heat sink would be bigger than that. I think they get away with the smaller size because the fuse amperage probably reflects only the pump motor starting current, its running current is probably a good deal less, and it normally runs for only a few seconds at a time. So the numbers in my example should be considered only that, and probably not what you'd see with a meter there in real life.

    So the purpose is that relay 1 can give you a slower, quieter pumping action, when the full pump speed from relay 2 isn't needed.
     
  17. Michciu94

    Michciu94 Junior Member

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    Brake Assu replaced for used one and for now everything works fine. No lights, Linear Valve Offset went fine first time.

    Old brake assy have resistance between BM1 and BM2 - 1500 Ohm and short circuit BM1 and GND1 so that was a fault.
     
  18. ChapmanF

    ChapmanF Senior Member

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  19. Michciu94

    Michciu94 Junior Member

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    I have drive with that used pump for 10 days and I have a question.

    This pump is quieter than old broke.

    My question is how often pump is turning on when driving and how much Volts is dropping when you press brake when car don’t drive?

    for me it drops about 0,2V every brake press and I think I hear pump every 2-4 pedal brake depress - it is normal ?
     
  20. ChapmanF

    ChapmanF Senior Member

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    I haven't really watched the pressure sensor voltage per brake press, but the pump every 2 to 4 uses does seem roughly in line with my experience.