ABS light stays on with ABS 11 fault code

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Weswolf, Nov 2, 2016.

  1. Weswolf

    Weswolf Bobtail Member

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    May 19, 2015
    Wilmington, NC
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    I have a 2011 Freightliner Cascadia with a solid ABS light that stays on after start-up and never goes off. I also have an ABS 11 fault code (SPN 793). From what I can gather on the internet, this fault code is referring to my Left 3rd axle wheel speed sensor. I would like to check the sensor but I'm wondering if I'll need to remove the tire first? I can see where the wiring goes inside the axle but the area where the sensor is located appears to be enclosed/out of reach.
    Anybody have any experience with this or know how to access the ABS wheel sensor?
    Thanks!
     
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  3. Heavyd

    Heavyd Road Train Member

    7,751
    6,184
    Feb 4, 2009
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    Any ABS sensor works about the same. If you can find where the sensor plugs into the harness, you can unplug it and then get a digital multimeter and measure A/C volts coming from the sensor as you spin the wheel by hand. Spinning the wheel by hand as fast as you can spin it should generate an A/C voltage of about 0.6 to 0.9 volts or more. This one test checks the sensor itself and if it is close enough to the tone wheel on the hub. If the sensor is no good, you will no voltage at all. If the sensor is ok, but too far away from the tone wheel, your A/C voltage will be very low, usually 0.3 volts or less. Typically ABS sensors are also about 1500 to 3000 ohms of resistance through them.
     
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  4. thodges

    thodges Light Load Member

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    Jul 13, 2014
    daytona beach,florida
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    So what wad the result?how much did it cost?
     
  5. GrapeApe

    GrapeApe Road Train Member

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    Jan 7, 2013
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    You should be able to get an FMI from your dash on that truck, might have to hit a button on the display for the next screen to get it. The SPN is only telling you which sensor, the FMI will tell you the type of failure. It could be a sensor or wiring issue. Or it could something more serious like a wheel bearing issue making the sensor gap too large. The FMI can narrow that down a but more and eliminate a few possibilities.

    But to answer your question, you will have to pull the wheels and brake drum to get at the sensor if need be, but you can check ohms and a/c voltage output without pulling the wheels. I generally ohm it out where the sensor plugs into the harness, if that checks out, then ohm it out again at the ECU plug, which will tell you if you have a wiring problem in the chassis harness.
     
  6. thodges

    thodges Light Load Member

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    Jul 13, 2014
    daytona beach,florida
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    So take it by a shop to have fixed.
    Is it something i should be alarmed to getting fixed immidetly? Or can i wait another week until I'm home.
     
  7. 9Toedtodd

    9Toedtodd Bobtail Member

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    Sep 8, 2022
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    Fail 5
     
  8. 9Toedtodd

    9Toedtodd Bobtail Member

    2
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    Sep 8, 2022
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