Cummins isx code 559

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by nitram1222, Mar 22, 2023.

  1. nitram1222

    nitram1222 Bobtail Member

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    Jan 4, 2014
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    My 2016 Peterbilt 579 with Cummins ISX throwing code 559 only when I go uphill with gas pedal on the floor (55mph-75mph). First both check engines light ( with the wrench and regular one) are on and if I put foot down from gas pedal check engine with wrench immediately disappear and only the other amber check engine stays on. If there are no hills for example 2 days regular check engine disappear also. I checked with computer and it is showing inactive code 559.
    I tried to replace both filters , pressure relief valve and fuel pressure sensor . Nothing helps so far . Anyone knows what can be the issue? My fuel pump was rebuilt 70 000 miles ago . Now I got 580 000 miles on engine . Overhaul on engine was done at 535 000 miles .
     
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  3. Ridgeline

    Ridgeline Road Train Member

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    You need a new fuel pump, the plungers in it need to be replaced, that's what the 559 code usually means - reduced rail pressure iirc
     
  4. nitram1222

    nitram1222 Bobtail Member

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    Jan 4, 2014
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    I was afraid I will need a new fuel pump. Truck is running fine with light on or off right now.
     
  5. gokiddogo

    gokiddogo Road Train Member

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    You need to read every word of the first post at this link, read it immediately, not after breakfast or at the end of your next work day, this is almost the exact same thing happening to you - your engine may be ready to self destruct and that is no exaggeration -

    Rawze.com: Rawze's ISX Technical Discussion and more - Havig a bad day. CM2350 fuel pump failure.
     
    RunningAces Thanks this.
  6. Goodysnap

    Goodysnap Road Train Member

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    Your fuel pump is going to explode and ruin your engine!!!!!!

    Stop reading bull crap on the inter web, stop throwing parts at the problem and pay a professional that knows how to troubleshoot the problem and fix the truck correctly.

    It could be anything from a cracked pickup tube to needed injectors and everything else in between.
     
    QUALITYTRUCK Thanks this.
  7. nitram1222

    nitram1222 Bobtail Member

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    Jan 4, 2014
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    Anyone knows good professional for this in Southwest of Chicago?
     
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