99 379 looking for ecm fuse wiring diagram

Discussion in 'Peterbilt Forum' started by simonsocm, Aug 15, 2021.

  1. simonsocm

    simonsocm Light Load Member

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    I've got a 99 379 with a series 60 and none of the wiring diagrams I've found seem to coincide with the ecm wiring on this truck.

    I stopped at a loves last night to change my coolant level switch and coolant temp gauge and must've jostled something behind the dash because afterwards my ecm didn't have power but the ecm fuse was good and had power.

    I've wired up a harness from the battery for now but I want to fix it properly once I get home.

    Is there any diagram that anyone has that'll show the ecm switched power circuit?
     
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  3. MLC Adventures

    MLC Adventures Medium Load Member

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    So you had all dash power, but wouldn't start?
     
  4. Ridgeline

    Ridgeline Road Train Member

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    Go to the dealer, give them your vin and have them print off the wiring diagram for your truck.
     
  5. simonsocm

    simonsocm Light Load Member

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    Had everything but the ecm plug at the ecm didn't have power and the ecm fuse did on both sides. I'm sure I probably just accidentally unplugged something but it's a rats nest of wiring behind the dash.
     
    MLC Adventures Thanks this.
  6. simonsocm

    simonsocm Light Load Member

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    Is that something they'll do for free? Or close to it anyways? Been a bit of a tight month for me because of repairs.
     
  7. Ridgeline

    Ridgeline Road Train Member

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    It should be free, it is a courtesy thing but if you can’t afford $50 for it …
     
  8. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    If you install an inline fuse in the wire that you installed and heat shrink/zip tie it properly you will be better off for the next time that you have a potential ecm power issue problem.
     
  9. simonsocm

    simonsocm Light Load Member

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    I actually had stuff on hand to throw an inline fuse, a switch, butt connectors good 3m electrical tape and convoluted tubing.

    So it's half decent at least.
     
  10. simonsocm

    simonsocm Light Load Member

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    Aug 17, 2019
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    Found the issue.

    There's a silver box up on the firewall on the passenger side of the engine bay that houses the two ecm fuses. There's a wire terminal block where they connect to the wiring from the battery before going to the ecm fuses then to the ecm. The wire terminal block was completely corroded.
     

    Attached Files:

  11. simonsocm

    simonsocm Light Load Member

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    Aug 17, 2019
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    I wanted to post the terminal that I used for anyone else that has a similar issue. The two post terminal is no longer available at Peterbilt and the original company no longer makes them. Painless Performance makes literally the exact same 2 post terminal however. I found mine on amazon. Part # is 80112 and they call it a junction block.
     
    Ky Flash Thanks this.
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