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Yellow Break warning light On dashbord 5 second after motor start

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Lars1595, Mar 20, 2023.

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  1. Lars1595

    Lars1595 Junior Member

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    I get the Yellow regenerative brake system warning light On dashbord 5 second after motor start i get it if I stand still or driving. The breaking works great and I get charging arrows to the battery and I have full break fluid and shifted pads and disc about 6 month ago. I have the torq lite with Odb and I don’t get any error codes on it. Can I troubleshoot some more in my own our should I drive to the mechanic.
     
    #1 Lars1595, Mar 20, 2023
    Last edited: Mar 20, 2023
  2. ChapmanF

    ChapmanF Senior Member

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    #2 ChapmanF, Mar 20, 2023
  3. Lars1595

    Lars1595 Junior Member

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    I charge the battery it was on 11v but I still have error on the dashboard. got sone error code from diagostic are these code relevant?
     

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    #3 Lars1595, Mar 21, 2023
  4. mr_guy_mann

    mr_guy_mann Senior Member

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    No those codes aren't relevant. They are only used for diagnosing the infotainment system and its databus.

    You need to use the mentioned procedure to pull "flash codes" for the braking system.

    Or, you can get a more capable scantool that can talk to the 15 or 16 ecu's present in a Gen2 Prius. Here's a thread that reviews several scantool apps and devices for smartphones.
    https://priuschat.com/index.php?posts/3290690

    Posted via the PriusChat mobile app.
     
    #4 mr_guy_mann, Mar 21, 2023
  5. SFO

    SFO Senior Member

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    Did you install the required gen2 "PIDs" in Torque?
     
    #5 SFO, Mar 22, 2023
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    Torque still won't talk to the ABS on a Gen2 (at least it didn't work for me on my 2006) ECM, hybrid control, HV battery, - some - but nothing else.

    Posted via the PriusChat mobile app.
     
    #6 mr_guy_mann, Mar 22, 2023
  7. Lars1595

    Lars1595 Junior Member

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    I went to the mechanic and got my Prius diagnosed the error code is u0126 it's lost communication with the steering wheel sensor.
    He thought I would have to replace the steering wheel senor module and he would need to call Toyota here if they have the part in stock and get back to me with a price estimate.
    But I was wondering is there something I could do to verify it the steering wheel sensor is actually broken or could it be some glitch in the wiring? Just want to make sure if there might there be a more affordable solution to check first
     
    #7 Lars1595, Mar 22, 2023
    Last edited: Mar 22, 2023
  8. ChapmanF

    ChapmanF Senior Member

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    That's good thinking, and the troubleshooting steps in the repair manual do have you check the wiring first, so if you follow those you should have the bases covered.

    Toyota Service Information and Where To Find It | PriusChat

    (I cheated and looked up the steps in a Gen 3 manual that I have closer at hand, so it would be better to follow real Gen 2 steps, but the ideas are probably the same.)
     
    #8 ChapmanF, Mar 22, 2023
  9. Lars1595

    Lars1595 Junior Member

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    Hi I found good step by step videos on youtube about how to remove the steering wheel and I measured the voltage on the white cable which I assume is the for the steering angel sensor module.
    I don't know the pin setup for the connector so I realise that I have no idea what I'm doing. But I could find pins with 11v and 5v so there is some power in the cabels.

    I put it all back to gather and I still have the same warning so not sure what should be the next step. Should I try to order a refurbished steering wheel module? I have seen some cheap one on ebay or is it another web site that is better for buying refurbished Prius parts.

    The mechanic shop that runs the diagnostic tool is still trying to get a hold of a new steering angel sensor module and give me a price estimate.
     

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    #9 Lars1595, Mar 27, 2023
    Last edited: Mar 27, 2023
  10. ChapmanF

    ChapmanF Senior Member

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    It sounds like the youtube videos weren't good enough or step by step enough to tell you what you needed to know; if you look up the troubleshooting steps in the repair manual, it will show you which pins are where and what to measure and what that will tell you.

    Toyota Service Information and Where To Find It | PriusChat
     
    #10 ChapmanF, Mar 27, 2023
  11. Lars1595

    Lars1595 Junior Member

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    I belive i found the right cabel it’s the gray and it have +11 v on pin 1-2 and -11v on pin 2-3.
    So i will try order a used on on and see if works
     

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    #11 Lars1595, Mar 27, 2023
  12. Lars1595

    Lars1595 Junior Member

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    Replaced the steering angel sensor module with one i found used on the internet. Installed it and got the exact same warning on the dashbord ⚠️5 second after i start the car. Not sure what to do now.
     
    #12 Lars1595, Mar 30, 2023
    Last edited: Mar 30, 2023
  13. ChapmanF

    ChapmanF Senior Member

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    #13 ChapmanF, Mar 30, 2023
  14. Lars1595

    Lars1595 Junior Member

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    I bought myself the mini vci with techstreamer and pluged it in and I can not see any steering angel sensor values on the emps view. I don’t even se a row for the sensor values. So the sensor must not send any values.
     

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    #14 Lars1595, Apr 17, 2023
  15. ChapmanF

    ChapmanF Senior Member

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    Although the steering angle sensor is attached to the steering wheel, it is not used by the EMPS system. It is used by the vehicle stability control, so you should see it in the data list for ABS/VSC/TRAC.
     
    #15 ChapmanF, Apr 17, 2023
  16. Lars1595

    Lars1595 Junior Member

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    Thanks found the value now and it says 1143 deg so it’s right out wrong. Could I try recalibrate my sensor module? Or is it broken
     

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    #16 Lars1595, Apr 18, 2023
  17. ChapmanF

    ChapmanF Senior Member

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    It will always say something goofy like that before you drive. The ECU auto-calibrates to the sensor reading while you are driving.

    The auto-calibration for this sensor depends on the correct calibration of the car's yaw and acceleration sensor (there is a manual procedure for that, which you do when the car is stationary on a level spot), and properly operating wheel speed sensors.

    Once you are driving, and the yaw sensor is saying no yaw and the wheel speeds are not different, the ECU says to itself "we're going straight right now, so whatever the steering angle sensor says right now is 0°" and it remembers that, and then what you see as the angle sensor reading will become sensible.

    But if you have just turned the car on to connect a scan tool and read the value, something nonsensical like 1143° is not unusual to see.

    You can go through the yaw and acceleration sensor calibration, but that's normally not needed, unless that sensor has been replaced. (It's down under the center console.)

    Did you mention what trouble codes Techstream is showing? Never mind, I see it right in the screenshot. So that was a freeze frame.

    If that communication code keeps coming back, then clearly there is an issue with the sensor or the wiring connecting it to the ECU. And in that case, the angle reading shown in the data list has not even anything to do with what the sensor is saying, because the ECU can't communicate with it.
     
    #17 ChapmanF, Apr 18, 2023
  18. Lars1595

    Lars1595 Junior Member

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    Thanks for the help. After changing the clock spring and steering angle sensor I was able to clear the code u0126 and I can see yaw values and I see steering angle sensor values when I drive above 25 mph. But there is something weird no with my steering wheel. Its 40 degrees off the steering wheel is centred when parked but after the first turn it gets completely off.
    I have done zero point calibration with techstream and papper clip. After doing the zero point calibration I got c1345(linear value offset) but if I did a linear value calibration with Teachstream it did disappear. So I'm not sure what the issue is here. I have change to summer tiers. Could that affect the steering that much?. Or is the clock spring with steering angle sensor installed wrong?
    Added a picture showing how off the steering wheel is when driving straight
     

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    #18 Lars1595, Apr 28, 2023
  19. dolj

    dolj Senior Member

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    My guess is the steering shaft turned between the time you removed the steering wheel to when you reinstalled the steering wheel.
    What exactly is the 'Techstream and paperclip' method you mentioned?
     
    #19 dolj, Apr 28, 2023
    Last edited: Apr 28, 2023
  20. Lars1595

    Lars1595 Junior Member

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    Is there a way to check if the steering shaft have been move? or should I just try to remove the steering wheel and then move the steering shaft in opposite direction and check the result?

    The Techstream is a diagnostic software and paper clip method was a method for short circuit the odb port pin 4 and 12 to trigger a zero calibration.
     
    #20 Lars1595, Apr 28, 2023
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