Options in lieu of replacing brake actuator?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PVL, Jun 3, 2020.

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  1. PVL

    PVL New Member

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    Hi all. 2006 Prius. Brake actuator went bad 2018. Brakes still function. I drive short local trips using extreme care and ready to apply parking brake if necessary. Do not have funds to replace actuator. Have been driving for two years with good braking. But now, the continuous cycling of the brake actuator is draining a brand new 12V battery completely down within 8 hours after turning off the engine. Other than the obvious options of replacing the actuator or junking the car are there any options to disconnect the failed actuator from draining the 12V battery. At this point I don’t care if the hybrid batteries stopped working as long as the Prius would still operate on gas only. Again, the brakes continue to function even though the actuator does not. Due to the serious nature of this issue, braking, I would appreciate comments from those that have technical knowledge on whether the actuator can be bypassed from the 12V system. Thank you.
     
    #1 PVL, Jun 3, 2020
  2. SFO

    SFO Senior Member

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    Welcome to PriusChat!!

    Thought about disconnecting the 12v battery to prevent it from draining?

    How old is the 12v battery, and what is the measured voltage at the battery and at the jump points under the hood?
     
    #2 SFO, Jun 3, 2020
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  3. ChapmanF

    ChapmanF Senior Member

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    It won't.
     
    #3 ChapmanF, Jun 3, 2020
  4. George W

    George W Senior Member

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    If you turn off SKS, will the actuator be working as much?
     
    #4 George W, Jun 3, 2020
  5. PVL

    PVL New Member

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    Thank you ChapmanF. Good to know that the Prius will not run as a gas only vehicle.

    Thank you SFO. yes, I have the 12v positive terminal off to preserve the battery from draining but I don’t want to do this on a continuous basis. I want to know if I can disconnect the brake actuator to prevent recycling and draining the 12v. battery.

    Hi George, sorry, SKS abbreviation for?
     
    #5 PVL, Jun 3, 2020
    Last edited by a moderator: Jun 3, 2020
  6. TMR-JWAP

    TMR-JWAP Senior Member

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    Not that I'm recommending it, but have you thought about spoofing the system so it thinks pressure is good all the time? Good pressure = no need to run the pump....or..

    Have you tried removing these two relays to see if the car is still functional (?). These relays should prevent the brake motor from starting. Not sure if it will allow car operation or not if one or both are removed. Make sure car is powered off prior to removing or installing.

    Motor relays.jpg
     
    #6 TMR-JWAP, Jun 3, 2020
    Last edited: Jun 3, 2020
  7. George W

    George W Senior Member

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    Smart Key System. You're Prius may not have that option . If you did, the brakes start pressurizing when the car detects that the fob is near. Turn SKS off, button located under steering wheel, and then the brakes won't pre-activate prior to the car starting.
     
    #7 George W, Jun 3, 2020
  8. ChapmanF

    ChapmanF Senior Member

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    This is a Gen 2, though?

    Of all the Prius generations, Gen 2 is the one you least want to be in with a disconnected actuator. You're left with completely power-unassisted brakes acting on the front wheels only. Everything else that system can do is handled electronically via the actuator.
     
    #8 ChapmanF, Jun 3, 2020
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  9. JC91006

    JC91006 Senior Member

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    Used brake actuators are getting quite pricey now, and they are not guaranteed to work after you install them. So if you are serious about keeping the car, you might have to put in a new unit for $1200-$2000 or it's time to say bye bye to that car.
     
    #9 JC91006, Jun 3, 2020
  10. T1 Terry

    T1 Terry Active Member

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    I'd go with installing a contactor on the 12v positive cable that you can turn on/off via a remote toggle switch located some where easy to reach. You could even add it to the drivers side door lock, but you would have to unlock the door with the key each time because there would be no 12v power supply to the central locking until the drivers door was unlocked.

    T1 Terry
     
    #10 T1 Terry, Jun 4, 2020
  11. fuzzy1

    fuzzy1 Senior Member

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    By federal passenger car regulations, the brakes mush still function even with complete failure of the power assist system. Mind you, this will be in old-fashioned manual brake mode, with severely increased braking distances despite very high brake pedal forces, effectively your entire body weight.
    That is how the Honda IMA hybrid system works. But not the Toyota hybrid system, which can't even start the gas engine.
     
    #11 fuzzy1, Jun 4, 2020
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