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Help needed with brake codes

Discussion in 'Gen 2 Prius Main Forum' started by BYUFam1, Jul 4, 2022.

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  1. BYUFam1

    BYUFam1 Junior Member

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    I have posted previously about an issue:
    Any help finding a Prius mechanic outside a stealership? | PriusChat

    Here is basic background. Had a periodic beeping occur. Some brake lights came on the dash. Then had some pulsing in the brakes when depressing them which eventually had periods of less than acceptable braking.

    I read through this forum and some other online resources and it appeared to me that it was likely the brake actuator.

    I took it to a place that said they could work on a Prius for that potential issue. They had me bring it into the shop they ran the codes and came back to tell me it was the Brake ECU and they could not do the work because they couldn't reprogram the ECU once it was replaced.

    So I went and bought an ECU did the work to replace the old one. Bought the Vxdiag VCMI and subscribed to TechStream for 2 days. Did the ECU reprogram, and all the available calibrations, cleared all codes and drove fine for a period of time. After initial test driving I ran codes again and these 2 kept coming back during that two days I had TechStream active.

    C1345 Not Learning Linear Valve Offset
    C1368 Linear Valve Offset

    But overall it was running fine then a few weeks/month later it was back to beeping and pulsating, etc.

    QUESTIONS:
    Does anyone know what I should be targeting with these 2 codes?

    Was it likely (if I am back to square one) that this was never the Brake ECU in the first place?
     
    #1 BYUFam1, Jul 4, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    As you have Techstream, have you run the linear solenoid offset learn procedure? If you haven't, well, "please run that" is what the codes you have mean.

    If you have tried that procedure a few times and it just won't learn, that's a different story. It does happen sometimes.
     
    #2 ChapmanF, Jul 4, 2022
  3. BYUFam1

    BYUFam1 Junior Member

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    I believe I have done that. I walked through every screen and did every task I could possibly find. And while this was a couple months ago now (been busy with Summer stuff while the car has sat) I do believe one of the options was the linear offset although I can't recall if the word solenoid was a term used.
     
    #3 BYUFam1, Jul 4, 2022
  4. SFO

    SFO Senior Member

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    #4 SFO, Jul 4, 2022
  5. ChapmanF

    ChapmanF Senior Member

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    It's worthwhile to be sure. A C1345 is normally about the easiest "problem" in the world to solve, as it just means "please run the learning utility" and one you've done that (with the proper preconditions from the repair manual met, like parking brake off), you're all set.

    But sometimes there's a bum actuator that just won't learn a proper offset with any amount of trying. Nobody likes that news.
     
    #5 ChapmanF, Jul 4, 2022
  6. BYUFam1

    BYUFam1 Junior Member

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    "Parking brake off" umm...don't believe I have done it that way :-(

    I will subscribe again to TechStream and give that a try.

    Is it just the link above for those pre-conditions or is there more I should be reviewing?

    [edit - I actually do not see a note about "parking brake off" in the doc linked above so any help on here to find that and any other pre-condition info would help.]
     
    #6 BYUFam1, Jul 5, 2022
    Last edited: Jul 5, 2022
  7. BYUFam1

    BYUFam1 Junior Member

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    No I unfortunately do not. I will have to look for them when I re-subscribe to TechStream.
     
    #7 BYUFam1, Jul 5, 2022
  8. BYUFam1

    BYUFam1 Junior Member

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    Updated and re-subscribed to TechStream and here are the codes I am currently getting:

    C1252 Hydro-Booster Pump Motor
    C1256 ACCumulator Low Pressure
    C1345 Not Learning Linear Valve Offset
    C1368 Linear Valve Offset
    C1391 Abnormal Leak of ACC Press

    I did run the various ECU reset, etc including the Linear Offset with it in neutral this time but it never seemed to get to the point where the lights would rapidly flash as it says it should.

    Hopefully I can get some additional quick advice before my 2 day subscription expires. Thanks in advance.
     
    #8 BYUFam1, Jul 5, 2022
  9. SFO

    SFO Senior Member

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    See if one of the 'posts' at this link can help with that limitation : https://blog.obdii365.com/tag/toyota-techstream/
    Are you able to search and find the workups for the obd2 codes being offered, or do you need some assistance?

    When techstream offers an obd2 code (DTC) with a snowflake to the left of it, click on the snowflake (freeze frame data) to find/locate the related 3 digit subcode (AKA : detailed code, or INF). Knowing any related subcode(s) may help in isolating and potentially fixing the issue in a timely manner.

    [​IMG]

    [​IMG]

    [​IMG]
     
    #9 SFO, Jul 5, 2022
  10. ChapmanF

    ChapmanF Senior Member

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    Probably need to follow up on the C1252, C1256, C1391 first. I don't think the solenoid offset can be correctly learned if the supply pressure is out of control.
     
    #10 ChapmanF, Jul 5, 2022
  11. BYUFam1

    BYUFam1 Junior Member

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    I was not getting the pressure codes before...but I also back then did not know to have the parking break off when I tried to do the offset.
     
    #11 BYUFam1, Jul 5, 2022
  12. BYUFam1

    BYUFam1 Junior Member

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    I had some issues with the software the first 2 days I used TechStream back in May (kept losing my registration code - something about windows defender messing with the files in the folder or something) and didn't get around to trying to look up remaining 2 codes until after it expired. I just determined that it looks like you can only search and get the PDF docs for those codes while your license is active. I have now found all of those PDF documents.

    I'm just not sure I understand them enough yet to do this work myself. I will try to look at the detailed/INF codes to see if it will further help me figure things out.

    Still open to any additional advice folks have.
     
    #12 BYUFam1, Jul 5, 2022
  13. BYUFam1

    BYUFam1 Junior Member

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    Just checked none of the remaining codes have a snow flake associated with them.

    [Edit - I was looking at the codes in the stored data file - I may have to reconnect to the car to see that other view you shared to see if there is a snow flake or not]
     
    #13 BYUFam1, Jul 5, 2022
    Last edited: Jul 5, 2022
  14. douglasjre

    douglasjre Senior Member

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    I had to do the linear valve calibration procedure seven times before it took effect. It was quite concerning but it worked eventually.
     
    #14 douglasjre, Jul 5, 2022
  15. douglasjre

    douglasjre Senior Member

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    C-1391 is the dreaded accumulator problem
     
    #15 douglasjre, Jul 5, 2022
  16. mr_guy_mann

    mr_guy_mann Senior Member

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    So, normally when you press on the brake pedal, there is no direct connection to the hydraulic calipers and cylinders at the wheels. Instead sensors let the braking control ecu know that you want to slow down, and how fast. That ecu talks to the Hybrid Control ecu.

    The HC ecu decides how much braking is done via regeneration - charging the HV battery, and how much is done via hydraulic friction brakes. The ABS/VSC/EBC (braking) ecu uses solenoid valves to direct high pressure brake fluid to the friction brakes.

    A pump forces fluid into an accumulator (a reservoir with high pressure gas behind a diaphragm. Fluid pushes on the diaphragm, compressing the gas further. So the accumulator stores a volume of high pressure fluid).

    A sensor monitors pressure in the accumulator. As the system uses fluid to stop the car, pressure (& the sensor voltage) drops. When the sensor goes to 3.2-3.1V, the ecu turns the relay on that supplies power to the pump. As the pump runs, pressure (& voltage) rises. At around 3.6V it shuts off.

    Ideally, the pressure should stay stable until you use the brakes. My 06 will have accumulator voltage drop by 0.02V over 20-30 minutes just sitting.

    If there is a leaking valve or something inside the ABS actuator assembly, pressure can bleed off over time without you using the brakes. That means the pump will run periodically to recharge the accumulator. As the leakage gets worse the pump runs more frequently. The ecu monitors pump run time and will set pump motor and accumulator leak codes if the pump runs too long or too frequently(ie, can't reach or maintain the 3.6V limit to keep the pump off.)

    There can be a fault where the accumulator loses some of its gas charge, so it can only provide a small volume of fluid before pressure drops. This would cause more frequent pump operation, but only after using the brakes.

    You can have an internal leak, or a failing pump, or a bad pressure sensor. All of these would require replacing the brake actuator assembly.

    There might be an external wiring fault for the accumulator pressure sensor (PACC) circuit (backprobing the circuit at the actuator should give a voltage reading that matches the data PID in Techstream).

    Or possibly a fault with the 2 large power and 2 ground wires that supply the pump - should read with a couple tenths of a volt of whatever the "12V" system is at when the pump is on and running.

    Posted via the PriusChat mobile app.
     
    #16 mr_guy_mann, Jul 6, 2022
    Last edited: Jul 6, 2022
    douglasjre likes this.
  17. dolj

    dolj Senior Member

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    +1

    (Just in case you got distracted.)
     
    #17 dolj, Jul 6, 2022
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  18. BYUFam1

    BYUFam1 Junior Member

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    So it seems like my initial searching of this site about it being something with the brake actuator is likely right and I have been down a rabbit hole because some neighborhood shop read an ECU code and I took them as more of an expert than my web diagnostic efforts :)

    How hard is it really to replace a brake actuator in a 2004? Sounds like a Toyota dealership thinks it starts at about $4k to replace...which is another reason I was more than happy to try the ECU fix/replacement on my own to start with...
     
    #18 BYUFam1, Jul 6, 2022
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  19. BYUFam1

    BYUFam1 Junior Member

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    Not distracted, just crossing some t's and dotting some i's on detail people asked about. Now overwhelmed with trying to figure out if replacing the brake actuator is in my wheel house or not.

    I'm wondering...my son had a little fender bender where a lady hit him. Pretty much all we did was bend the fender around the front passenger tire a little and accept that the metal from the door and the fender make a noise when opening/closing the door. (this was great because I was able to start hearing when my son would get home as I heard the door - I never heard the car before because it was so quiet :) ) Is it possible that the fender bender jostled or damaged the brake actuator and I could get her insurance to pay for fixing it?
     
    #19 BYUFam1, Jul 6, 2022
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  20. BYUFam1

    BYUFam1 Junior Member

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    Brake actuator has been installed. I have pumped the brakes and heard the actuator do its compressions and stop. I dis several pumps to the floor until it was tight and no longer made noises at the different wheels and the actuator.

    I then attempted to start the vehicle (one of the videos I watched suggested that) and I get a death triangle and other lights.
    20220720_124049.jpg
    I also get a new warning on the console screen.
    20220720_124053.jpg

    One of the videos even did a test drive at this point while others suggested a manual bleed and another to use TechStream to do a bleed amd other utilities.

    I was going to move the car to another part of our property to get a better Internet signal for using TechStream and it won't go into reverse or drive.

    At this point I have not reconnected the windshield wipers but everything else appears to be back in the right place and fully connected.

    Is the TechStream utility functions all I will need now or is there something else I need to be addressing first? I don't want to start a 2 day license if my car is not ready. Any help would be appreciated.
     
    #20 BYUFam1, Jul 20, 2022
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