Cannot complete replacement brake booster air bleed procedure

Discussion in 'Gen 3 Prius Technical Discussion' started by George Jung, Oct 31, 2025 at 9:04 PM.

  1. George Jung

    George Jung Junior Member

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    Ive tried everything to get the air bleed procedure to complete but it is not working.
    I replaced the master cylinder and abs accumulator a few months ago and have not been able to do the bleed procedure.
    I bought a 50 amp charger, im reading 14 volts when i try to start the procedure and its still not working.
    I got the vxdiag cable. I was trying to use it with techstream 18, Ive now signed up for the toyota two day subscription ands its still not working
    I also have a code for steering angle sensor. I replaced the clock spring with steering angle sensor twice with used oem ones from ebay and steering angle sesnor is still not reading, it always reads 850.5.
    I checked the voltage and resistance checks for the l51 connector that is said to do in the manual, its still not working. Ive attached the DTC's im getting.
    Im so desperate to get this to work, ill do anything, somebody please help.
     

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    #1 George Jung, Oct 31, 2025 at 9:04 PM
  2. ASRDogman

    ASRDogman Senior Member

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    50 amps??? OUCH! That is WAY too much for the 12v battery. 5 amps is enough.
    What device are you using for the procedure? Is it an aftermarket techstream cable? If so, that is
    likely your issue. It's common. Some say there is a certain cable to buy to get it to work.

    alteck has a tool, I'm not familiar with it, but others are. I have the D8Tools device that is very good.
    I'll be using it when I do the brake job in the future.
     
    #2 ASRDogman, Nov 1, 2025 at 8:05 AM
  3. Brian1954

    Brian1954 Senior Member

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    Did you buy a new or used part?
     
    #3 Brian1954, Nov 1, 2025 at 9:31 AM
  4. George Jung

    George Jung Junior Member

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    New. I've verified it was the correct part number.
     
    #4 George Jung, Nov 2, 2025 at 12:59 PM
    Brian1954 likes this.
  5. George Jung

    George Jung Junior Member

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    I've tried multiple cables. Nex IQ USB link 3 ($800 adapter for heavy duty diesel) , the vxdiag vcx nano, i tried using my friends scan tool, with all of them i immediately get and "air bleeding failed" message when i try to start the procedure. Ive verified that the parking brake switch is showing on, brake pedal switch showing off, etc. I do notice that some of the accelation/deceleration sesnors are displaying a non zero value when the car is stopped and i'm trying to do the procedure? could this be causing it to fail?

    Also i should note that a few months back i had blown the 125a fusible link and bypassed it.. Not sure if that would have any impact because i am reading 14 volts in tech stream not in ready mode when i have the charger connnected.
     
    #5 George Jung, Nov 2, 2025 at 2:53 PM
  6. ASRDogman

    ASRDogman Senior Member

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    I seem to remember someone saying the car had to be on, but not ready? I'm not really sure.
    It was a while ago.
    Perhaps search prius chat for that procedure and you'll find the issue.
    A lot of people seem to have a similar issue. Usually it's because of a pirated copy of techstream,
    and/or cable.
    Maybe try it with the parking brake off? Or the opposite of where it is while your bleeding?

    I think you can just do a regular bleed procedure, instead of going through the whole thing again.

    I don't know about the other sensors. But since you have the scan tool, you want to check why
    they are showing zero, and if that is normal or not.
    Obviously, you should check all the wiring to make sure nothing is damaged.

    You can get the Xtool D8 (and now D9) for less than $800.
     
    #6 ASRDogman, Nov 2, 2025 at 4:44 PM
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