C-15 mbn lower boost than normal

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Robertstrucking2285, Jun 23, 2022.

  1. Robertstrucking2285

    Robertstrucking2285 Bobtail Member

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    Jun 23, 2022
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    I have a 379 with the c-15 mbn a couple weeks ago it started missing bad while accelerating, replaced wiring harness under valve covers and went through the harness from ecm to the rocker box. Replaced the ecm and #6 injector. Runs a lot better now but something still isn’t right. Loaded and full throttle I can only get about 22 pounds of boost through any of gears, truck had more power before this started. I hook up the truck to computer and shows no codes but if I do the diagnostic using the cruise control it shows boost pressure sensor fault atmospheric pressure sensor fault and at one point it showed injector 3 or 4 fault. Any ideas on the next step I should try? I don’t have the money to just start buying parts and it not fix it. Thanks so much for any help.
     
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  3. baha

    baha Road Train Member

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    You need to replace the pressure sensor it can make truck run bad when it gives wrong information like the truck is on top of rocky Mt out W. or at sea level when you are on top of Mt. to the ecm ?
     
  4. Robertstrucking2285

    Robertstrucking2285 Bobtail Member

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    Jun 23, 2022
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    I run Louisiana Mississippi and Texas
     
  5. Magoo1968

    Magoo1968 Heavy Load Member

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    Odds are you had a non bridge program before and new ecm has a bridge program which many including myself find very lazy.. find some to flash a 6nz program into ecm and it should wake up.
     
    spsauerland Thanks this.
  6. lester

    lester Road Train Member

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    I drove an MBN that wouldn't build boost past 22lbs as well. It's the crappy mbn tuning and electronic turbo actuator. Different tune and getting rid of the electronic actuator will do wonders.
     
    Magoo1968 and spsauerland Thank this.
  7. Robertstrucking2285

    Robertstrucking2285 Bobtail Member

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    Jun 23, 2022
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