DEF warning problems

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by LVSS, Feb 23, 2020.

  1. LVSS

    LVSS Bobtail Member

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    Feb 23, 2020
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    I’ve got a 2018 Cummins 325 on an international 4300. The DEF tank is full and I just changed the fluid filter. At some point every day the alarms go off and degrades the engine to 5mph. I can drive for a mile or two and it goes away. I checked the electric connections and they are all good. Any ideas?
     
  2. AModelCat

    AModelCat Road Train Member

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    Unless you can tell us a fault code all we can do is spitball. There's literally dozens of faults that can throw a derate.
     
  3. LVSS

    LVSS Bobtail Member

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    Feb 23, 2020
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    Active
    SPN 3521 FMI 31
    OC 3

    Past
    SPN 3364 FMI 10
    OC 19

    SPN 5246 FMI 0 and 16
    OC 9
     
  4. Goodysnap

    Goodysnap Road Train Member

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    Jul 12, 2017
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    I would say with faults you have listed, you most certainly have an issue with the DEF quality/level/temp sensor or wiring to the sensor. Prior to 2017 DEF quality was calculated by the NOx sensors. 2017 and after OEM's were required to add an actual sensor in the tank to measure DEF quality to prevent tampering.

    So far they have been less than reliable and have a high failure rate. Check with your OEM for possible warranty. Some components are covered under 5yr 100K federal warranty.

    Good Luck!!!!!!!!!!!!
     
    Dale thompson, magoo68 and Heavyd Thank this.
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