ABS Relay 1 problem - brake accu?

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

  1. Michciu94

    Michciu94 New Member

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    Hello. Ive got C1252 and C1256 error sometimes. Ive tried to make Linear Valve Calibration and it doesn’t make - few days ago the motor works when calibrate but today is not working. I’ve checked via Techstream and Motor Relay 2 works and pump is running - Accumulator Pressure is rising but Motor Relay 1 don’t work. I’ve make it ON via Techstream but no pump running. The Relay is OK, voltage on relay socket 12V so it’s OK. Now I Have to go to brake acculator and check resistance and then on Skid ECU or it means that I need change brake accu or brake ECU?
     
  2. ChapmanF

    ChapmanF Senior Member

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    Does the Motor Relay 1 click when you tell Techstream to activate it?
     
  3. Michciu94

    Michciu94 New Member

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    I’ve just checked it and it clicks so as I understand diagram problem is at Brake Accu?

    I will have to check BM1 and 3 pin at Relay 1 but BM1 is hidden. Is there easier way?
     
    #3 Michciu94, Sep 17, 2022
    Last edited: Sep 17, 2022
  4. Tombukt2

    Tombukt2 Senior Member

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    So in this condition does the car start does the car ready does the car have all the amber lights on like the brake pump is bad just curious? With no noise from the pump I would assume you have a very hard pedal or no brakes at all or you need two people to stand on the pedal or something when my accumulator was failing I had all the amber lights on on the dash but my pedal was great and I drove for almost a year like that until it finally completely failed.
     
  5. Michciu94

    Michciu94 New Member

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    Car start, I can drive but I have 3 icons on Dashboard, hard pedal and no recuperative breaking + beeping sound. When I use few times Motor Relay 2 test in Techstream, the pump is running and beeping sound gone, but it came back because Motor Relay 1 doesn’t start the pump and there is no pressure in accumulator.
     
  6. Prius1mil

    Prius1mil New Member

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    Can you post a picture of the skid ecu? I am having an issue and was wondering if it's the same. I also have blink code.

    My codes are (!) 52 and 57. ABS 42.
    What does it mean?
     
  7. Tombukt2

    Tombukt2 Senior Member

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    Sounds about right mine was running all the time but wasn't making good pressure in my '05 so I had a hard pedal that two people had to stand on to stop the car so we stopped driving the car. Then in my '09 the same thing was happening The pump was running a lot not all the time but when I get out of the car I'd be in the house and hear it still running before it cut off 2 minutes something and all the lights were on on the dash that normally come on for the accumulator or the big brake problem where the pump is always running. At that point I still had a good pedal and everything was working basically as it should but the pump running a lot this went on for almost a year and a half and then a caliper failed and then the brakes failed except for one caliper in the front working. And at that point I changed out the accumulator actuator right behind the inverter and then all the lights went away and everything worked like when I first bought this 09 model car and I've left it alone since then I did not bleed with tec stream or any of that .
     
  8. ChapmanF

    ChapmanF Senior Member

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    dolj answered that question for you in your other thread, here.
     
  9. Michciu94

    Michciu94 New Member

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    In my problem pump is not running now - relay 1 have issue as described earlier so what I have to do next ?
     
  10. ChapmanF

    ChapmanF Senior Member

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    If it were my car, and I confirmed the relay was clicking, I would be looking in the wiring diagram to see the path for motor current through that relay, to see if I could use my meter and find the first point where the voltage did not appear. If the voltage appeared all the way to the brake actuator but the pump did not run, I would conclude the problem was within the actuator assembly. (In a Gen 2, there's no strong need to distinguish the actuator from the accumulator, as that generation combined them in one assembly anyway.)

    Toyota Service Information and Where To Find It | PriusChat
     
  11. Michciu94

    Michciu94 New Member

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    Ive had a Wire diagram. It have a voltage in PIN5. The MR1 and MR1+ works because the relay is clicking. Next is BM1 but it is in Brake Accuator plug, which is in very hard place to reach. Maybe someone know other place to check it?

    as I’m good read diagram - if BM2 works then BM1 should also work after get 12v so it will be broke PIN3 or some short circuit in pump? As I said it is very hard to get to those Pump harness to check.
     

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  12. ChapmanF

    ChapmanF Senior Member

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    Naturally, if you've confirmed voltage at the relay pin 5, it would make sense to next confirm voltage at pin 3 when the relay is closed.

    If that is confirmed, then A2 pin 2 would be the logical next place to check. Yes, it may be in a hard place to reach. But certainly less hard than replacing the actuator assembly, which would be the next step if you don't check for a wiring fault first. And the work of reaching it is part of the work that would be necessary for actuator replacement.

    The benefit of checking the wiring first is it saves you the effort and expense of replacing the actuator if the actuator isn't the problem.
     
  13. Michciu94

    Michciu94 New Member

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    Hmm. Is there any possibility to check relay socket? I don’t have a workshop to remove windshield etc to get to pump wires :(

    can someone say how fast voltage drops at Accumulator when you increase pressure to about 4.0V?
     
  14. ChapmanF

    ChapmanF Senior Member

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    The windshield does not need to be removed for access, only the windshield wipers and the cowl. This is a step that is at the start of so many procedures under the hood that it is like "chop one onion" at the start of a recipe. I don't do it in a workshop, but in my driveway. :)

    When the brake system is in good condition, the drop of pressure when the brakes are not used is very slow, on the order of hours.
     
  15. Michciu94

    Michciu94 New Member

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    Hmm, so maybe I will try doing this and check the wiring from relay to pump. The 12V have to miss somewhere becouse motor is running good with Relay 2, and looking for schema it is very weird if in BM1 is a Voltage and motor don’t run.

    So I think I will go to the car, pump the pressure and then check how many V drops overnight - it will be a good test to see if I need whole pump or only regenerate the motor/electronic of pump which is mounted.

    If it will drop much I will have to change pump in spite of all yes? It is called ,,internal leakege” yes? But I don’t remember that motor turn on often when IDLE. I remember the motor often turn on when I came to crossroad and using brakes.
     
  16. ChapmanF

    ChapmanF Senior Member

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    If you think about it, the schematic is a drawing of the system when it worked. What happens when something fails is that, somewhere in the car, something has become different from what the schematic shows. Whether that's in the wiring outside the actuator, or the wiring or connections inside the assembly, it's still weird when you're looking at the schematic.

    Hmm, I have only just noticed that the diagram you posted does not show the motor resistor. The difference between the motor 1 and motor 2 circuits is that circuit 1 includes a resistor (so relay 1 is used to run the pump at a quieter speed). The resistor is located inside the cabin, under the dash, near the left corner under the windshield.

    What you posted came from the repair manual, where simplified wiring drawings are often included in diagnostic sections for convenience. They are sometimes missing details from the actual wiring diagrams, which are in a separate manual.

    Your diagram shows the green wire from the relay pin 3 routed directly to A2 pin 2.

    In reality, the green wire runs through the firewall to pin 2 of connector IP1, whence a black wire continues to pin 2 of B19 (the resistor). From pin 1 of the resistor, a white wire runs back to IP1 (pin 1) where it becomes a pink wire that runs to A2 pin 2.

    So a few things more to check.

    In this thread, you will see that post #39 describes how to reach the resistor with less work than removing the dash top:

    brake actuator resistor | PriusChat

    Internal fluid leakage, by the way, isn't always a problem with the pump. There are many valves inside the actuator, which can eventually fail to seal completely when closed, leading to pressure loss.

    In a Gen 2, it is not especially important to distinguish between pump/accumulator/actuator problems, as they are all one assembly. In Gen 3 it becomes more important, as there is a choice of which assembly to replace.
     
    #16 ChapmanF, Sep 18, 2022
    Last edited: Sep 18, 2022
  17. Michciu94

    Michciu94 New Member

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    it is this point at schema right?

    As I can see the resistor have blue connector with two black wires so I have to check if there is a pass between those two and also check if 12v is going to resistor socket from motor relay. As I can see it can be dissembled without dash remove.

    But internal leakage is very common issue, and I think the error occurs when those value go below about 3V, and in my case it’s maybe becouse motor not always turn on when nessesary - I will check how much voltage drop overnight.
     

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  18. ChapmanF

    ChapmanF Senior Member

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    Yes, that's the animal.
     
  19. mr_guy_mann

    mr_guy_mann Senior Member

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    I would remove motor relay (1) and check voltage at pin 3 when motor relay 2 is commanded on. If BM1 and the resistor are ok, then you should have 12V at pin 3. If that is ok then I would carefully jumper relay pin 3 to 5 and see if the pump runs.

    Posted via the PriusChat mobile app.
     
  20. Michciu94

    Michciu94 New Member

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    Ive checked some things.

    First, after a 14h voltage on accumulator sensor drops from 3,76V to 3,66V so I think it is pretty ok?

    Next I checked resistance between PIN3 of Relay 1 and Relay 2 and the result I show on the photo - it is OK? I think I need to check resistor right becouse it’s way to high?

    When I take off Relay 1 then computer see C1253 code and I can’t activate Relay 2 so I can’t check voltage on PIN3.
     

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    #20 Michciu94, Sep 19, 2022
    Last edited: Sep 19, 2022
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