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VSC etc lights, C1236 code

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by 1954oval, Feb 7, 2018.

  1. 1954oval

    1954oval New Member

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    Have an intermittent VSC, ABS and ! lights. It'll go off and stay off for 20-30 miles at times and other times will stay lit for 20-30 miles. Lights originally popped right after I bought the car, took it home and pulled code for C1236 debris on tip of sensor. Didn't notice any particular debris but I cleaned the sensor, inspected and cleaned the sending ring with brakleen and reinstalled. Thought that fixed the issue but it popped up again about 20 miles into the first couple of drives.

    I thought about buying a new sensor, but I found one at the junkyard for 6 bucks. Installed, cleared code and it repopped pretty soon afterwards. It's possible I had two bad sensors, but they're fairly robust so I'm a little suspicious and disinclined to spend $200 on something that at this point I'm thinking probably won't fix the problem.

    Freeze frame data showed the same speed reading on all 4 wheel sensors, and nothing out of the ordinary, so I'm not really sure what other diagnostic tests to perform. I have the Techstream software.

    As I see it, I'm looking at 1. sensor actually being bad, 2. wiring harness inside wheel well being bad, 3. sensor ring being bad, or 4. wheel bearing being bad which could be causing an erratic reading from the sensor.

    1 & 3 seem unlikely to me after replacement of sensor, and visual inspection of ring. Intermittent nature makes me think 2 is unlikely, but I'm open to it. Unsure if 4 would cause the issue, and if it wouldn't have other codes.
     
    #1 1954oval, Feb 7, 2018
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  2. bisco

    bisco cookie crumbler

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    welcome! how many miles on her?
     
    #2 bisco, Feb 7, 2018
  3. 1954oval

    1954oval New Member

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    Thanks!
    95k miles, also potentially related, the traction control seems somewhat more sensitive than I would expect. Triggering over even small bumps sometimes.
     
    #3 1954oval, Feb 7, 2018
  4. padroo

    padroo Senior Member

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    There is a YouTube video showing them troubleshooting an ABS sensor. They found a broken wire or intermittent wire at the first clamp on the rear wheel sensor. You have Techstream, you should be able to rotate each wheel and watch the count on your screen but while doing that do a wiggle test on the wiring. Those sensors live in a really bad environment. I would inspect each connector by disconnecting it and look for green stuff and make sure each connection is good.
     
    #4 padroo, Feb 7, 2018
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  5. 1954oval

    1954oval New Member

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    Thanks, I'll check it out, I checked the connectors and hit 'em with a little DeOxit, but I'll give it another look see.
     
    #5 1954oval, Feb 7, 2018
  6. bisco

    bisco cookie crumbler

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    tc is pretty sensitive, how long have you owned her?
     
    #6 bisco, Feb 7, 2018
  7. padroo

    padroo Senior Member

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    Here is a link showing one of the problem areas.

     
    #7 padroo, Feb 7, 2018
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  8. 1954oval

    1954oval New Member

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    This car only a few hundred miles, had another 2007 that my mom totaled back in September and don't remember it being quite so sensitive, but it could be something like different grippiness of the tires or tired suspension
     
    #8 1954oval, Feb 7, 2018
  9. Kevin_Denver

    Kevin_Denver Active Member

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    To me it sounds like #2 is the most likely cuase. I can tell you as an electrical engineer that a wire that's broken internally would connect and disconnect intermittently with the jostling of a car. I would try cleaning and inspecting the connector first. Often wires break internally right next to connectors/securing points. I might try disconnecting, cleaning, and reconnecting every connector between the sensor and ECU.

    How I understand most speed sensors work is that they detect it each time one of the little "lobes" in the middle of the rotors passes, then knowing the number of lobes, it can calculate the RPM of the wheel, which can be translated to speed by knowing the wheel diameter. Therefore I wouldn't expect a wheel bearing to affect the speed sensor unless the bearing was really bad (which would be noticeable). However if you have an very worn or warped rotor this could cause bad readings.

    I take it the car drives and brakes at medium to high speeds without vibration or unusual noises?
     
    #9 Kevin_Denver, Feb 7, 2018
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  10. padroo

    padroo Senior Member

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    I believe they use a square wave if you happen to have an ocilloscope, the distance from what I understand is a tone ring is critical. I agree, all connectors need to be taken apart and inspected.
     
    #10 padroo, Feb 8, 2018
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  11. 1954oval

    1954oval New Member

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    I tore it apart again on Saturday, and it's quite subtle, but I'm pretty sure I've located the problem. I was reluctant to accept a wiring issue because I think there are codes that correspond to broken wire/resistance out of spec, but I pulled the wheel off to check. I figured I'd give the tip junkyard sensor a quick scrubdown with a brass brush and give the wheel a little scrubbing to get rid of some light corrosion and salt residue. Unlikely to be a major issue, but since it was intermittent, I figured every bit helps.

    It was very subtle, but I'm pretty sure I've found the problem:

    Doesn't look like the tone ring is available separately for this gen Prius? I may go to the junkyard and see if there's an axle I can drift it off of, or I guess drop a reman in just for convenience. I'll probably have a poke around later to see how much of the suspension I have to tear out to get the axle R&R'd
     
    #11 1954oval, Feb 11, 2018
  12. ChapmanF

    ChapmanF Senior Member

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    Hard for me to be sure just what your picture is a picture of ... do you think that tone ring has been dislodged from its normal position? Possibly having to do with the corrosion of the shaft?

    -Chap
     
    #12 ChapmanF, Feb 11, 2018
  13. thesaint

    thesaint Junior Member

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    oval,
    National Tire and Battery has told me that the CV shaft is next for me. my c1236 came on after a bad mechanic installed a hub assembly on my driver front wheel and didn't put the bearing cover/ tone ring cover back on. since then I have replaced both hub assemblies and the steering rack. I buy my own parts and have mechanics put them in. I cant help but think they are breaking other things because they are not getting profit on my parts just their labor rate. anyways i still have the code and lights and no fix. I hope this can help you and I hope that someone can help me. I have been trying to get this problem fixed for many months and am getting tired of the problem.

    I have a new 12v battery and still have the c1236 and dash lights.

    i have 252,000 miles on my 07 touring prius. my vsc is also super sensitive.

    I don't think its the tires or suspension. I have new struts and good tires on my car. Its something else i think.

    no, I don't think so.
     
    #13 thesaint, Sep 18, 2018
    Last edited by a moderator: Sep 19, 2018
  14. thesaint

    thesaint Junior Member

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    I need a proper diagnosis and repair with my parts if possible. please let me know if anyone can help me.
     
    #15 thesaint, Sep 18, 2018
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