W900 ecu problems

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Bmoore98, Apr 23, 2026 at 10:19 PM.

  1. Apr 23, 2026 at 10:19 PM #1
    Bmoore98

    Bmoore98 Bobtail Member

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    Hey guys. My old man drives a 1998 w900. N14 cummins with an 18speed behind it. We took the truck in after the transmission grenaded. Since then the speedometer hasn't worked. So we replaced the sensor. Still nothing, gentleman at the shop said to try another ecu. So we plugged that ecu in. Mind you, it's not throwing a single code. But the speedometer still isn't working, the fan won't shut off, and the cruise control won't work either. It still idles up when you turn it on, but when driving it won't hold a speed. Anyone had similar issues?
     
    Bmoore98, Apr 23, 2026 at 10:19 PM
    Bmoore98, Apr 23, 2026 at 10:19 PM
    #1
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  3. Apr 23, 2026 at 10:32 PM #2
    MRMTRANS

    MRMTRANS Medium Load Member

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    Is the sensor positioned close enough? I'd check current in the sensor wires too. These are simple and can do yourself. Otherwise, I'd think you could hook a laptop with diagnostic software and start troubleshooting from there.
     
    MRMTRANS, Apr 23, 2026 at 10:32 PM
    MRMTRANS, Apr 23, 2026 at 10:32 PM
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  4. Apr 23, 2026 at 10:39 PM #3
    Star Rider

    Star Rider Road Train Member

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    Pull the sensor out and stick your finger in the hole and see if you feel the teeth on the tone ring, they might have not swapped it from the old trans.
     
    Star Rider, Apr 23, 2026 at 10:39 PM
    Star Rider, Apr 23, 2026 at 10:39 PM
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    Oldman83 and 062 Thank this.
  5. Apr 23, 2026 at 10:42 PM #4
    Star Rider

    Star Rider Road Train Member

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    upload_2026-4-23_22-42-29.jpeg
     
    Star Rider, Apr 23, 2026 at 10:42 PM
    Star Rider, Apr 23, 2026 at 10:42 PM
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    Big Road Skateboard Thanks this.
  7. Apr 24, 2026 at 6:30 AM #5
    Big Road Skateboard

    Big Road Skateboard Road Train Member

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    I don't think the yoke would ever tighten if it wasn't in there? The bearings never would anyway.

    But yeah, I'd look for a loose yoke. If that ring isn't tight, or worse, missing, it'll never work.

    Also make sure the wiring to the VSS didn't get between the bell housing and flywheel housing.
     
    Big Road Skateboard, Apr 24, 2026 at 6:30 AM
    Big Road Skateboard, Apr 24, 2026 at 6:30 AM
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    Star Rider Thanks this.
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