C1235 - Foreign Object is Attached on Tip of Front Speed Sensor RH

Discussion in 'Gen 2 Prius Technical Discussion' started by tonicacent, Dec 14, 2024.

  1. tonicacent

    tonicacent Junior Member

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    I have a 2008 Prius with 115k miles.

    Bad front hub assembly was replaced on front RH. ABS VSC light comes on at exactly 63 MPH after about 5 seconds. Codes turn off under 63 within 10 minutes. Regenerative brakes occasionally switch to hydraulic at 15 MPH and the car lurches forward.

    The car has been to my mechanic 4 times now to try and fix with no luck. The hub was upgraded and replaced again, and the speed sensor was replaced. Everything was checked for debris.

    I see a few threads with the same issue, but no real solutions. It's been two months of trying to figure this one out, and I'm ready to throw in the towel.
     
    #1 tonicacent, Dec 14, 2024
  2. Tombukt2

    Tombukt2 Senior Member

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    Do you have anything called codes they generally begin with p or c or other letters and have four digits or so after them That's what you need from all these mechanics that are telling you all these things everybody tells people all these things but doesn't give them the codes kind of interesting to me and why people wouldn't ask is quite interesting You kind of sort of need the codes to help get you in close to the troubleshooting you need to do other than that you just really guessing debris on the end of the sensor so on and so forth I'm assuming people have looked on the end of the sensor to make sure there is no debris it's magnetic It will pick up Ferrous metals. Is the tone ring which you can see through the hole that the sensor goes in in the aluminum hub with a flashlight when you rotate that tone ring around does it all look uniform any teeth are broken or anything like that You're going to have a problem.
     
    #2 Tombukt2, Dec 15, 2024
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  3. mr_guy_mann

    mr_guy_mann Senior Member

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    The brake control ecu sets that code when it sees an "abnormal" signal from the right front sensor. It could be something like a damaged toothed tone ring on the axle shaft CV joint.

    Really, I would want to use an oscilloscope to view the signal waveform, then I would know what's wrong. Especially since the left front sensor works fine - there's a "known good" signal for comparison..

    Unfortunately very few shops have a scope or techs who can use one.

    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Dec 15, 2024
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  4. tonicacent

    tonicacent Junior Member

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    Didn't mention the left front wheel hub was replaced at the same time with no issues.

    To be honest, I no longer trust this mechanic. He said it was fixed two times now with his tech driving to 65, 75, 85 with no code. I've been watching the dash light up EVERY time I hit 65 for 2 months. Really nice guy, and he has been doing his best to help without additional costs. Need to look for someone with a little more expertise.
     
    #4 tonicacent, Dec 16, 2024
  5. tonicacent

    tonicacent Junior Member

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    No codes except C1235.
     
    #5 tonicacent, Dec 16, 2024
  6. tonicacent

    tonicacent Junior Member

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    So is the tone ring is apart from the hub assembly?
     
    #6 tonicacent, Dec 16, 2024
  7. Tombukt2

    Tombukt2 Senior Member

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    Yes it's on end of drive axle it shoved into the big hole on rear of hub assy . Which is why you can't see it when it's all installed except by taking the sensor out using a flashlight and somebody rotating the axle so you can see all of the cuts If anything is broken or messed up there's your problem that tone ring there are stepped cuts in it and it has to be exactly the same all the way around If one of those cuts is missing or broke off because of sloppy installer removal work then there will be your issue or if it's greased up or dirty and it can't see the cutouts same situation
     
    #7 Tombukt2, Dec 17, 2024
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