ABS Booster, accumulator, stroke simulator trouble

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by DentedKnight, Feb 16, 2024.

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  1. DentedKnight

    DentedKnight New Member

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    I replaced the brake accumulator and I'm going through the Brake Bleed portion of the repair. I have an Autel MaxiCOM MK808BT Service Tablet. The problem I'm running into is what I believe is too much pressure on the Stroke simulator as it is reading .82-.84 without any pressure applied to the brake pedal. The prius is reading this as constant brake pressure (rear tail lights on and when trying to go to IG-ON no ready, it starts the car as if I'm pressing the brake).

    What is the default standard V reading for the stroke simulator?
     

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    #1 DentedKnight, Feb 16, 2024
  2. Tombukt2

    Tombukt2 Senior Member

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    Wild I have to refer you to the factory manual which is pasted away somewhere and all this site but I have no idea what the strokes emulator pressure would be at rest with no foot on the break I hope it would be like near zero. And if that's the part that's connected to the pedal on the firewall if it's all electronic then more than likely there's no way to control or mess with it probably isn't even if it's more or less manual or not electronic. Very strange though It's that part is electrical the stroke simulated that's creating the pressure what happens if it's unplugged I know all the lights and codes will come on for the brake system etc I was just wondering if the stroke simulator would be it much lower or near zero?
     
    #2 Tombukt2, Feb 17, 2024
  3. ChapmanF

    ChapmanF Senior Member

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    There's more going on here than stroke simulator pressure, because the rear brake lights and start button do not rely on stroke simulator pressure for their operation. They rely on the electrical pushbutton switch up near the pivot of the brake pedal.

    So that switch seems to be convinced the pedal is a little bit pushed. The stroke simulator pressure is a separate reading, but seems to agree.

    I would look closely over the linkage and the physical installation to find out why that pedal seems a little bit pushed.
     
    #3 ChapmanF, Feb 17, 2024
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  4. Tombukt2

    Tombukt2 Senior Member

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    Maybe somebody's adjusted the switch before or there's a spring undone or something when you're not on the break nothing should think that you are the switch none of it.
     
    #4 Tombukt2, Feb 17, 2024
  5. DentedKnight

    DentedKnight New Member

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    That's my theory too but I'm not sure where to start. Attached is a photo with the stroke sensor disconnected and the spring that holds to the clip that attaches the brake booster to the pedal. There are two holes on the pedal, I have it connected to the upper as that is what made logical sense.

    Would y'all agree that it would be something physical contact of the pedal and not pressure in the system or what not?

    What I did was I removed the brake booster and accumulator to fix the ABS (!) for the recall that this vehicle is out of warranty for, I just replaced the accumulator as it was the cheaper and most difficult part to replace which I verified fixed the issue until I started the brake bleeding process to "complete" the job so the brakes worked properly.

    The reason this is stopping me from completing the process is because it states I need to reset the ecb memory, turn off the car, go back into IG-ON, ready off, then run a linear offset. The problem is after turning the car off pressing the button, the next thing it does is start the car (which fails the linear offset). The only way to get it back into ig-on is to remove the battery positive connector wait 5min, and reconnect which if I do the linear offset at this point it runs through the process but does not do the final flashing that the process was completed.

    I'm open to any suggestions at this point.

    My next step based on this info would be to take the pin off the pedal and booster to see what the reading is.
     

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    #5 DentedKnight, Feb 18, 2024
  6. DentedKnight

    DentedKnight New Member

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    I disconnected the brake pedal and tried to run through the entire process again making sure to hold the pedal up to enable going into IG-On and no ready mode and it even though it said it completed the linear offset it still is throwing the offset codes.

    Any other suggestions before I give up and head to the dealership?
     
    #6 DentedKnight, Feb 20, 2024
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  7. Michael48

    Michael48 Junior Member

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    Was the problem with your stoplight switch adjustment? I replaced mine and have the same issue. I'm thinking the actuator pedal adjustment is different than my original pushing the switch to turn on brake lights
     
    #7 Michael48, Jun 16, 2024
  8. Tombukt2

    Tombukt2 Senior Member

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    I can't wait to hear what the dealer does to get this to work.
     
    #8 Tombukt2, Jun 16, 2024
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