"Peterbilt 348 w/paccar px-9 (2021)

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by ntorres041788, Dec 8, 2022.

  1. ntorres041788

    ntorres041788 Bobtail Member

    5
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    Dec 8, 2022
    Sun Valley, CA 91352
    0
    I have a Peterbilt with a px-9 engine which is what im assuming just the same as a L9 cummins with code
    spn 3521 fmi 18. im sure it is pointing out to be an issue with the def system. i have tested the def with a refractometer and it shows it is fine and did do a change in the def filter as well. has anybody else have an issue similar that can be of some help. i cleared the code but noticed it has returned..
     
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  3. bjytech

    bjytech Light Load Member

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    Nov 9, 2013
    Ohio
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    The quality sensor is part of the smart unit (tank level, temp, and quality) so generally it is either a DEF quality issue or the sensor is bad, which is common. they were on national backorder last I checked on one but its been a while, hopefully supply has gotten better.
     
  4. ntorres041788

    ntorres041788 Bobtail Member

    5
    0
    Dec 8, 2022
    Sun Valley, CA 91352
    0
    I was scared it would be that as i have already changed one in the past with our other trucks and they do not run cheap at all. considering it is such an extremely expensive part. i would of thought they would atleast fix the issue if its so common a part that goes bad..considering the costs..
     
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