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Prius Brake Questions - Regen? ABS Module?

Discussion in 'Gen 2 Prius Main Forum' started by horn12007, Sep 28, 2022.

  1. horn12007

    horn12007 Junior Member

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    This is more of a 2 headed threaded:

    1 - Just replaced the ABS module with a used one. Completed the Techstream ABS procedure. Drove the car 40 to 50 miles today (in town driving). The ABS still makes noise. Seemed like it got worse throughout the day. Car still stops fine and has good pressure. No lights on the dash though. Did a health check and NO CODES. I was thinking that I'd have a code if it's bad. I guess they can be going bad but not trip up codes? It seems that as long as I have the keys around the car, the ABS is pretty active with the noises.

    2 - Regen braking jerking? As I slow down and get to around 7mph and under the brakes seem to jerk/pulse. I could be creeping at almost 0 mph and it jerks a bunch. Not like a bad brake rotor. More like the brakes are being pushed quickly. I've been reading that Regen braking starts there and is probably the issue. Should this happen often? It seemed that about 20 miles into my 40/50 mile driving, it started to do this and would keep doing this. I would think that it'd do it that much.

    ***New Prius Owner with very minimal experience with these cars.
     
  2. fuzzy1

    fuzzy1 Senior Member

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    Regen braking should cease below 7 mph, giving you only friction braking at those low speeds.
     
  3. horn12007

    horn12007 Junior Member

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    hmmm. Guess I misread. Maybe I just need to replace the rotors/pads then. Just feels like the jerking is due to how quickly it happens.
     
  4. fuzzy1

    fuzzy1 Senior Member

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    When slowing down, the regen shutdown at 7 mph isn't always a seamless transition to pure friction braking of the very same strength. Sometimes with light braking and smooth pavement, I notice the transition as a momentary reduction or pause or change in braking. But this should happen just once when slowing, right at 7 mph, and be relatively mild.

    Your repeated pulsing or jerking, or when creeping at lower speed, does not sound related to this regen transition.
     
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  5. horn12007

    horn12007 Junior Member

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    Yeah. I'm just thinking it's a wonky abs actuator.
     
  6. horn12007

    horn12007 Junior Member

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    It's definitely not just a transition, it's a repeated braking thing.
     
  7. mr_guy_mann

    mr_guy_mann Senior Member

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    Do any lights come on when the brakes feel jerky? My first thought would be that a problem with a wheel speed sensor or tone rong is causing false ABS activation (but the Prius usually illuminates an amber indicator when the ABS system is active).

    I suppose you could monitor or record some ABS data while braking and see if any of the solenoids turn on - off quickly when the symptom appears.

    Posted via the PriusChat mobile app.
     
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  8. horn12007

    horn12007 Junior Member

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    No lights.
     
  9. ChapmanF

    ChapmanF Senior Member

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    Well, to be blunt, so what? The system does make noise. There's a pump in it. You haven't described your noise in any way, to tell us what you think is unusual about it.

    The pump should sound a little like a rattlesnake or a joy buzzer. You'll normally hear it every few times you use the brakes. You normally don't hear it very often if you are not using the brakes. What is yours doing?

    As for the jerky application of the friction brakes once you are going too slowly for regen, I might try a relearn of the linear solenoid offset.
     
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  10. horn12007

    horn12007 Junior Member

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    I meant significant ABS noise at all different times. Pretty safe bet it is bad.
     
  11. ChapmanF

    ChapmanF Senior Member

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    Like what kind of noise? Like the sound of the pump running? Repeatedly at times when you aren't braking?
     
  12. horn12007

    horn12007 Junior Member

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    The pump running often. like every 20 seconds it comes on for 5 or 10 seconds. Does it when i'm not braking and when I am.
     
  13. ChapmanF

    ChapmanF Senior Member

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    Yup, that actuator's done for.
     
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  14. SFO

    SFO Senior Member

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    Normal behavior.
     
  15. ChapmanF

    ChapmanF Senior Member

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    Every 20 seconds when not braking can be compared to "normal behavior" of every several hours. Easy comparison.
     
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  16. horn12007

    horn12007 Junior Member

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    Seems like it's making an extended amount of noises. Seems like it's about 50/50 when the key is around the car. Just seems extremely excessive.
     
  17. horn12007

    horn12007 Junior Member

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    Maybe I'm tired or just stupid but for some reason I don't understand what this means. lol.
     
  18. ChapmanF

    ChapmanF Senior Member

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    You're saying it seems extremely excessive. I'm agreeing with you.

    Here's what "normal" is: if the car is on, and you are not using the brakes, you might hear that pump noise once every several hours. I say again, several hours.

    Hearing it every 20 seconds? That is orders of magnitude outside of normal. That unit is done for.
     
  19. horn12007

    horn12007 Junior Member

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    oh. lol. I did immediately take a nap after your comment. For some reason I read that as you saying it was normal. ha.

    Yeah. Im surprised there are no lights on the dash. This one makes more noise than my old one. Probably driven it 200 miles like this. Oh well. new ABS here I come!
     
  20. SFO

    SFO Senior Member

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    How old is the 12v, and what is the resting voltage?