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ABS/Trac control light illuminated

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by 379Hoodlife, Mar 29, 2022.

  1. Mar 29, 2022 #1
    379Hoodlife

    379Hoodlife Bobtail Member

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    Mar 29, 2022
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    Ok, need some advise here. Peterbilt 379 2007. My abs/trac control lights are illuminated. Went to PB and replaced ecm for this system. They performed chug test on all pressure modulator valves. Tested resistance on pmv wires, all were in spec. Performed voltage checked on pmv, all in spec. All good no more lights, park up for the night, next day when to start truck and abs/trac control lights on again. No chug test from pmv. Could the pmv be bad or shorting out? Any advice would be greatly appreciated.
     
    379Hoodlife, Mar 29, 2022
    379Hoodlife, Mar 29, 2022
    #1
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  3. Mar 29, 2022 #2
    FLHT

    FLHT Road Train Member

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    Should be a reset button in the top of map pocket.
    Push in and ABS light should blink.
    But light will not go out until you get moving.
    May have to shun down motor and restart.
     
    FLHT, Mar 29, 2022
    FLHT, Mar 29, 2022
    #2
  4. Mar 30, 2022 #3
    379Hoodlife

    379Hoodlife Bobtail Member

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    Where is the map pocket located?
     
    379Hoodlife, Mar 30, 2022
    379Hoodlife, Mar 30, 2022
    #3
  5. Mar 30, 2022 #4
    FLHT

    FLHT Road Train Member

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    In front of shifter little cubby its inside
    push button up
     
    FLHT, Mar 30, 2022
    FLHT, Mar 30, 2022
    #4
  7. Mar 31, 2022 #5
    Heavyd

    Heavyd Road Train Member

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    When you are dealing with any electronic module like this, the first step is to always check for fault codes. Having a light on can mean literally anything. In order to help you better we need to know at least what code is getting logged.
     
    Heavyd, Mar 31, 2022
    Heavyd, Mar 31, 2022
    #5
    spsauerland Thanks this.
  8. Mar 31, 2022 #6
    379Hoodlife

    379Hoodlife Bobtail Member

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    When it first happened and taken to a PB dealer it had a 12-7. Don't know what it is now, just assuming same fault as before since it reappeared.
     
    379Hoodlife, Mar 31, 2022
    379Hoodlife, Mar 31, 2022
    #6
  9. Mar 31, 2022 #7
    Heavyd

    Heavyd Road Train Member

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    If you have a Bendix system, Bendix is very sensitive to shorts to ground. They have to check all the PMV leads to chassis ground. Everything has to be totally open to ground. Even resistances in the mega ohm range will cause this fault. The Bendix ECU is unable to pin point which modulator common is shorted, so the all have to be tested. This also includes the traction control valve if equipped.
     
    Heavyd, Mar 31, 2022
    Heavyd, Mar 31, 2022
    #7
    spsauerland Thanks this.
  10. Mar 31, 2022 #8
    379Hoodlife

    379Hoodlife Bobtail Member

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    Mar 29, 2022
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    They tested all pmv's, ground , resistance and power all checked good. They didn't test the tcv, where is that located? My 379 has this feature, in tried pushing the trac switch but nothing happened. Light stayed on.
     
    379Hoodlife, Mar 31, 2022
    379Hoodlife, Mar 31, 2022
    #8
  11. Apr 1, 2022 #9
    Heavyd

    Heavyd Road Train Member

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    The traction control valve is built into your rear brake relay valve. Look for a relay valve with a wire harness coming from it.
     
    Heavyd, Apr 1, 2022
    Heavyd, Apr 1, 2022
    #9
    spsauerland and 379Hoodlife Thank this.
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