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ABS/VSC/Trac Warnings w/ DTC

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by wlai, May 1, 2018.

  1. wlai

    wlai Junior Member

    Joined:
    Sep 22, 2007
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    Location:
    Pacific NW USA
    Vehicle:
    2008 Prius
    Model:
    Touring
    Hi: I've searched but couldn't find an exact match of my scenario, could use some help to verify the diagnosis:

    A. For weeks now when I drive home which is at the bottom of a hill and come to a stop, the red general warning light comes on for just a second momentarily. No OBDII code that I can find.
    B. Last Thur, I got the Brake/ABS/VSC triple and they stayed on. It would start normal, but those three would turn on a few minutes after start as I start driving, and stay on. Next start would be the same.
    C. In return I got the mVCI and Techstream scanners and pulled these DTC from the ABS/VSC/TRAC: C1311, U0123, U0124, U0126, U293. There was some "cloud" icon next to the C1311, and U0124, not sure what that signify.
    D. I also got B1271 Combination Meter DTC.

    <all the screens from Techstream are attached below for reference>

    From what I can gathered by PriusChat and looking thru my 2d subscription of TechInfo, these may be the issues:

    1. 12v Battery may be low causing the communication network to fail. I should try to measure voltage with lights off and with lights on, while ignition is off.
    2. The U-codes mean that there was a communication issue, so it can be the some sort of sensors along with ECUs issue, though all the different U codes probably mean it may be a wiring/harness issue as well.
    3. There is this "zeroing calibration" of the Yaw Sensor, which may be the issue of coming to a stop on a downhill stope. I may need to zero calibrate the Yaw sensor to see.

    Does that look right? This is the first time I used the tools and so I wasn't sure what I was doing exactly. Are there other things I should look on Techstream or Techinfo, to get to the bottom of the issues with all these codes?

    Also I'm surprised how complicated the Techinfo repair manual instructions are, it's not written at all for a home mechanic. Is the Haynes manual better for someone like me?

    Thanks for your wisdom!
     

    Attached Files:

    #1 wlai, May 1, 2018
  2. dolj

    dolj Senior Member

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    Location:
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    Vehicle:
    2007 Prius
    Model:
    N/A
    Not sure where you got the idea about the yaw sensor calibration.

    You need to focus on the C1311, but before you do that check that the 12 V is in good condition and fully charged. This is because one of the trigger conditions implies if the R1+ terminal has a voltage less than 9.5 V could be an issue.

    C1311 INF 1 (and C1312, C1313 and C1314)

    DESCRIPTION
    ABS main relay 1 (ABS NO. 1 relay) supplies power to the changeover solenoid and the linear solenoid. ABS main relay 2 (ABS NO. 2 relay) goes on for approximately 5 seconds after the power switch is turned off and the braking effort signal input is terminated. ABS main relay 2 (ABS NO. 2 relay) supplies electricity and maintains operating condition for the brake system when the power switch is OFF.

    C1311 detection conditions:
    When either condition below is met:
    • Relay contact is off (BS 1 terminal is less than 3.5 V) for at least 0.2 sec. when R1+ terminal voltage is 9.5 V or more and main relay 1 is on.
    • R1+ terminal voltage is less than 9.5 V and main relay 1 cannot be on for at least 0.2 sec. when main relay 1 is turned on (BS 1 terminal is 3.5 V or more).
    C1311 Trouble Area
    • ABS main relay 1 (ABS NO. 1 relay)
    • Skid control ECU
    • Harness and connector
    Step 1 of the inspection procedure has you run two tests for the proper functioning of the ABS NO. 1 and ABS NO. 2 relays.

    Not sure exactly how you go about finding the section for your code on TIS, but @ChapmanF is our wizard on TIS. It is all there on TIS, for sure on the RM tab.

    Hope that helps a bit.

    BTW, the "cloud" icon is actually supposed to be a snowflake and indicates there is freeze frame data (FFD). If you click on that icon, it brings up a snapshot of the datapoints at the time the code set.
     
    #2 dolj, May 1, 2018
    Last edited: May 1, 2018
    SFO and Raytheeagle like this.
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