Transmission fault while driving, Peterbilt 579

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mhlvc, Feb 20, 2024.

  1. mhlvc

    mhlvc Light Load Member

    May 2, 2020
    Current code in picture 1, and previous/history codes are in the 2nd picture.
    Any idea whats going on?
    Transmission fault popped up while driving on highway, didnt want to upshift, barely made it to parking. After clearing the code - nothing, same issue, unplugged batteries waited 15-20 min, same code popped up.
    Truck didn't want to go in R or D, kept flashing F, auto.
    Went under truck after visiting this page:

    Pushed the 2 connectors (3-Way Gen1 ECA Connector and the 1 above it) in a little and code went away - and was able to drive truck normally like everything was fine.

    What can be the issue here? Bad actuator? Bad clutch? Bad connectors? Bad fuse on the eca connector? Bad wiring?

    Attached Files:

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  3. JB7

    JB7 Medium Load Member

    Dec 13, 2022
    First thing to do would be to carefully check all the wiring coming from the transmission. Pull apart any connectors and look for corrosion. Even if no corrosion best to clean with a cleaner such as Deoxit and then use silicone dielectric grease before re-connecting. The Eaton website has complete diagnostic manuals that can be downloaded for free. The manual gives diagnostic procedures for each code. Almost 400 pages so too large to attach here. After checking the wiring and connections I would clear the codes and drive to see if any come back. May have just been a loose connection.
    The ECA was not getting the voltage it needs.
    The code in the 2nd pic, 520271 FMI 4. Your link tells what to check for that code and FMI 4.
    The ECA operates on a non-switched battery power supply.
    FMI 4 – Voltage Below Normal or Shorted Low:
    FMI 4
    • ECA Vehicle Harness
      • Damaged wiring between the vehicle batteries and 3-Way ECA Connector
      • Bent, spread, corroded or loose terminals
      • Wiring shorted to ground, shorted to power or open
    Last edited: Feb 20, 2024
  4. mhlvc

    mhlvc Light Load Member

    May 2, 2020
    So how wasnt it getting enough voltage? It happened twice that day while I was driving, thankfully 2nd time it happened (as I was on the highway) I was close to my parking and somehow made it without stopping, barely.
    When I pushed the 2 connectors in a little the code went away. After that I went under again and unplugged both of
    them, cleaned them with an electric cleaner, put some dielectric grease, plugged them back in and secured with zipties.
    Did a short drive with it and everything was fine, no issues. Hopefully I dont get the same issuue again when Im otr.
  5. Tanker312

    Tanker312 Light Load Member

    Apr 16, 2017
    I drive a Chevy Silverado, and I ran into a somewhat similar transmission issue last year. It started acting up on the highway, not wanting to shift properly, and then I got stuck with it not going into reverse or drive, just flashing symbols at me. After some trial and error, and almost thinking it was a major mechanical failure, I stumbled upon a solution that involved checking the connectors and wiring, much like you did.

    What really helped me diagnose and understand the issue better was using cummins software. This software gave me a detailed analysis of what was going wrong and pointed me towards a problem with the connectors and a potential wiring issue. After securing the connections and checking for any wiring faults, my truck started to run smoothly again.
    Last edited: Mar 16, 2024
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