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  1. #1
    JKR1300's Avatar
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    Code 54 & 66 - Stepping Motor

    My engine has been abruptly loosing power. All of a sudden no power, a few seconds later it runs great. Comes and goes. First time it happened I thought I lean seized. But then it runs perfect - normal RPM. Yesterday it finally picked up 2 trouble codes - 54 stepping motor malfunction & 66 stepping motor stuck closed.
    Late last year I had problems with the stepping motor. I also picked up code 66, but the problems was different - it would idle at about 2500 rpm. I replaced the stepping motor with a used one I got from Nate (N8R).
    Unfortunately the stepping motor is part of the throttle body assembly and is not replaceable on it's own.
    Looking at the wiring diagrams in the manual, the only circuit I found that use the stepping motor is the off throttle steering system. The off throttle systems is activated by the steering switch. This switch should not be active since I have UMI steering and the switch is just zip-tied in place. (it normally picks up the location of magnets on the stock steering stem).
    I have several questions:
    - does the stepping motor really serve a purpose other than the off throttle steering system.
    - Can it be disconnected or somehow bypassed
    - does anyone have an extra stepping motor they want to sell
    - The manual states that to check these systems you have to hook it up to the yamaha diagnostic software. Sould I take it to the dealer for diagnosis? I normally do all my own work. Will the ECM store this malfunction even after the code has been cleared.
    Not quite sure where to go from here.


  2. #2
    "Hustler" Inkaddict's Avatar
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    If the big plug on the main harness (where the efi controller plugs in) gets wet or coroded it WILL pull false codes... such as the one your getting... Ski will be fine and all of the sudden rich as fu*k and in limp mode... Spray the plug out with some electric cleaner and use some grease or silicone on the plug... I chased the same problem for over a month...

  3. #3
    JKR1300's Avatar
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    Quote Originally Posted by Inkaddict View Post
    If the big plug on the main harness (where the efi controller plugs in) gets wet or coroded it WILL pull false codes... such as the one your getting... Ski will be fine and all of the sudden rich as fu*k and in limp mode... Spray the plug out with some electric cleaner and use some grease or silicone on the plug... I chased the same problem for over a month...
    It's definately an electrical problem. And your right - when it bogs down it's getting full rich mixture - plugs are soaked. Getting to those main electrical plugs is a pain.

  4. #4
    "Hustler" Inkaddict's Avatar
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    Quote Originally Posted by JKR1300 View Post
    It's definately an electrical problem. And your right - when it bogs down it's getting full rich mixture - plugs are soaked. Getting to those main electrical plugs is a pain.

    Ski idles really low and shuts down when you let off the gas?? Theres a aersol spray called Pro Gold.. Its used in high end audio applications and prevents corrosion on terminals.. Alot of stand up jet ski guys use it as well.. I havent had any problems since using it.. Another thing to check is to make sure IF you removed the stock air tubes that the plug isnt hanging dirrectly under the ait intake under the farrings.. Thats how my plug was getting wet in the first place...

  5. #5
    JKR1300's Avatar
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    Idle is normal, engine does not stop

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