SBT Jetski Engines, Parts & Accessories

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  1. #1
    Joined
    Jun 2011
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    Default Knock sensor alarm on new SBT engine - 2004 Honda F12

    Just finished breaking in my new SBT engine and my FI alarm is going off with code 25 which indicates a "Knock Sensor circuit Malfunction".

    Here is some additional info:

    - Ran motor about 8 hours before the first alarm went off. No problem during break-in or for the first few hours of normal operations.
    - I can run it the next morning half an hour or so before the alarm goes off
    - If I disconnect the harness long enough for the display to time out. I can then restart it an run another 10-15 minutes before the alarm comes on.
    - The longer I let it sit after alarm, the longer it will run. As if cooling off seems to help.
    - I bought 30 gallons of 93 octane, this batch was used during breakin and for a few hours of normal running without the FI error, so I think the fuel is not the cause.
    - I never had this error on the old engine where the sensor originally came from. Granted I could have damaged it during transfer....

    I am going to order a new knock sensor, but are there other likely causes?

    Am I risking engine damage to run it until the knock sensor goes off, then the 1/4 mile back to the dock while the FI alarm is beeping?

  2. #2
    Joined
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    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    pre ignition will cause the sensor to trip, if the sensor is bad I would think it would be going off all the time. Put some octane boost in the tank, see if that helps.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

  3. #3
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    upstate, SC
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    3

    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    I just had the same problem with a knock sensor code 25. The unit was an 02 f12x. It had an all original engine with 134hrs. Replaced the sensor and 3 hes runtime later the wristpin on number 4 broke....at 6k rpm. Not saying that's what is wrong w yours but I would do a rod end play check to verify the sensor isn't picking up a rod knock. good luck

  4. #4
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    Tarpon Springs
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    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    very interesting because I am starting to worry it is the motor. This is what I have done/observed since then:

    - Added octane booster, it was fresh 93 octane if Shell is trustworthy. This had no impact.
    - Removed the pump coupler so that any bearing vibration from pump would be eliminated. This had no impact.
    - The sensor is going off sooner each time I start the engine, it now goes off within 5 minutes of run time.
    - The temp light was flashing this time along with FI light, the alarm code was still 25 (knock sensor)
    - When I first installed the engine it was smooth as silk at 5000 rpm, now it feels rough.

  5. #5
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    Jul 2011
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    upstate, SC
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    3

    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    Is the engine getting hot? Check your cooling lines for blockage, verify a good flow of water at the indicator on the rear port side. Also a misfiring spark plug can cause the knock sensor to trip. I'm sure you know those plugs are expensive but I would rreplace them anyway.

  6. #6
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    18

    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    When running from a hose got lots of water coming from the exhaust and the telltale stream looks normal. Plugs are new, replaced them with the motor. I have checked the plugs (multiple times now!) and all plugs look the same and they look good. Don't see any difference between cylinders.

    Thanks!

  7. #7
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    upstate, SC
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    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    Why did the original engine need to be replaced? What was the cause of failure? Were there any other codes showing or just the knock sensor?

  8. #8
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    Tarpon Springs
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    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    Well after replacing knock sensor and eliminated the coils, spark plugs, fuel and jet pump, all fingers are pointing towards a bad ECU. Had Honda dealer put it on computer and that is their conclusion also. Hopefully I can find a good used one because the best price I can find is $750

  9. #9
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    Tarpon Springs
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    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    Well I found a used ECU from 2007 F12 and it is running great, I am actually getting an extra 2 mph, cant explain why but I will take it! And I learned that the knock sensor alarm is a common symptom of a bad ECU.

    Tom, I want to thank you and the folks at SBT for going the extra mile to help me. Without going into details, SBT has proved to be a customer focused company that others could learn from. Often times the market leader gets arrogant and complacent, great to see that has not happened with you folks!

    Many Thanks!

  10. #10
    Joined
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    Default Re: Knock sensor alarm on new SBT engine - 2004 Honda F12

    Gary, it good to hear its working well, we are always glad to help.
    SBT Tech Support is here to help with your problems.
    We try to answer each question quickly and accurately.
    Please do not use Private Messaging for Tech Support, use the forums.

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