ABS MODULE LOCATION on 2017 Volvo VNL

Discussion in 'Volvo Forum' started by STS1SS, Apr 17, 2021.

  1. STS1SS

    STS1SS Bobtail Member

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    I'm looking for help location modules. In this case specifically the ABS module. We have an open circuit. Dealer wants to replace the entire harness. I want to check for broken or damaged cable, corrosion in connectors etc.

    2017 Volvo VNL.

    Any help is appreciated. Would like to find cable routing etc. as well if possible.

    Thanks,

    Joe
     
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  3. Socal Xpress

    Socal Xpress Road Train Member

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    Does it have a code?
    Where are you suspecting the break might be?
     
  4. STS1SS

    STS1SS Bobtail Member

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    SPN794

    The code is for the RR 3rd axle sensor..

    The sensor is ok. Dealer says break is in the harness.

    Rather than spend $400+, I want to look at connectors and the cable.

    Thx
     
  5. Socal Xpress

    Socal Xpress Road Train Member

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    The cheapest and fastest repair is to replace the harness. The harness main connector is under the cab near the air dryer.. Typically the back half is the easiest to have a break since it battles the elements. Now Volvo is known for crappy wiring. So you could spend more on chasing the break then what it will cost to replace the harness.
     
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  6. jason6541

    jason6541 Road Train Member

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    The actual brain is up under the dash above the dog house buried in the dash.
    The wheel speed sensor for that position may be faulty to big of a air gap to tone ring on hub. Corrosion in connector follow the cable from the wheel end and find connector. It is a Hall effect sensor
    Check the 2 pins probably just the sensor. But Volvo is known for electrical problems. Like all mfg’s they couldn’t put dielectric grease on connectors to prevent it. Also check up at the relay valve under or behind fifth wheel to check for corrosion. Been a few years since I looked at a Volvo
     
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  7. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    90% of rear abs problems occur in the harness in driver side frame rail between 1st drive axle and back of cab. When you cut zip ties to drop harness from air lines you will see that Volvo gives literally 6 extra feet of harness that is looped. I bet you find your corroded wire in that 6 feet of loop.............
     
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  8. nasriza

    nasriza Road Train Member

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    I wouldn't waste my time cheaper to install new harness i think harness cost should not be over $500 labor is a couple of hrs, and you are all good to go for a few years to come, to fix it its a gamble how long it will last more $$$ now but more savings down the line. Ask to only replace rear chassis harness not the whole chassis harness never seen one break in the front.
     
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  9. STS1SS

    STS1SS Bobtail Member

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    Ok guys... thanks.

    As to repair or replace. Replace is easier, but there are zero in north America.

    Provided its not a connector, I am an electronics technician and have made and repaired industrial cables for harsh environments for over 30 years.

    Since I originally posted we got a better explanation from the dealer. They tested the module, the "front cable", the sensor... all good. We also have an issue with rear diff temperature, so my guess is there's a break in that bundle of joy someone mentioned.

    I'll be after it this weekend and I'll report back.

    Thanks.

    It would be helpful if I could find pinouts for this thing. Any pointers there would be great.
     
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  10. jason6541

    jason6541 Road Train Member

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    Volvo truck website use to have manuals and such on website not sure if they still do. Parts dept or service May print you a specific schematic
     
  11. STS1SS

    STS1SS Bobtail Member

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    Ok. Found no damage but confirmed an open on the twisted pair to RR axle ABS sensor. Made up a twisted pair and replaced.

    ABS issue resolved.

    Now need to hope the other unrelated issues were somehow caused by this issue. Not optimistic... just hoping.
     
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