Eaton automated transmission code 25 persists

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by ZooX, Aug 28, 2023.

  1. Aug 28, 2023 #1
    ZooX

    ZooX Bobtail Member

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    Sep 8, 2019
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    2019 Peterbilt 389

    I have been trying to get rid of this code on ICU display for a long time. It just does not go away.
    Whenever I start the engine, it shows 25 which means it goes into product diagnostic mode. I tried replacing the ignition switch. What can I do next?

    With 25 displayed at all times, the driver does not know which gear he is driving at. 20220207_103207.jpg
     
    ZooX, Aug 28, 2023
    ZooX, Aug 28, 2023
    #1
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  3. Aug 28, 2023 #2
    Goodysnap

    Goodysnap Road Train Member

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    This is normal operation. When cycling the key 2 times the system is placed in Diagnostic mode or PD mode, so you can shake down the wiring to detect intermittent or hard to find issues.

    This will occur on a normally functioning truck with no issues.

    Maybe an internal TECU issue? Always displays 25 no matter what?

    I suspect the unit has a cranking issue where the driver is rapid cycling the key and causing the PD mode to occur.
     
    Last edited: Aug 28, 2023
    Goodysnap, Aug 28, 2023
    Goodysnap, Aug 28, 2023
    #2
    ZooX and krupa530 Thank this.
  4. Aug 31, 2023 #3
    ZooX

    ZooX Bobtail Member

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    Sep 8, 2019
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    Cranking issue could refer to the starter?

    Ignition switch solution was an official fix but did not work in my case.
     
    ZooX, Aug 31, 2023
    ZooX, Aug 31, 2023
    #3
  5. Aug 31, 2023 #4
    Goodysnap

    Goodysnap Road Train Member

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    Yes I would begin with a starting and charging system inspection. Clean and service batteries and load test.
     
    Goodysnap, Aug 31, 2023
    Goodysnap, Aug 31, 2023
    #4
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