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  1. #1

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    ECM Knock Sensor Bypass

    Since my ECM is bad rather than my knock sensor, and because I can't find a replacement 02 ECM, I'm going to have to find a way to bypass the code 25 shutdown. All the service manuals I can find give a pin layout and wiring diagram for the 04 and up which has the 2 plugs instead of the 3 plugs for the 02. can Anyone tell me which pin or wire color at the ECM is the knock sensor for a 2002. I don't really want to take the intake and intercooler all off just to see. I want to probe the signal to see if there is a pattern of voltages the ECM likes and those it switches to limp mode for.
    Thanks,


  2. #2
    AWA MEMBER
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    have you checked the harness? if the ecu has a internal fault from heat or wear, i don't see how you will bypass that

  3. #3

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    The harness seems fine, IE no obvious wears or knicks. I want to start up with my voltmeter probing the line. I should see a low range of ac voltage starting at idle and increasing as the rpms go up. If I see a clean signal then I assume its the ECM. From there I hope the ECM is just over sensitive. If it triggers consistently at a higher voltage I can either isolate the knock sensor or come up with something to simulate an acceptable voltage while I ride. I could care less about knock at this point. I just don't want to have to part out the ski. If anyone has been down this path before though let me know if I'm wasting my time.

  4. #4

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    Update, first to answer my first question, the knock sensor is wired via a solid blue wire to the center plug on an 02 ECM, I wired leads into the circuit and hooked my volt meter up so I could monitor the circuit while I rode. I read around 2.5 mv at idle and maxed the sensor out at 28mv riding. None of this however tripped an F1 code so I'm stumped. Maybe its intermittent so I left my lead setup in place and will ride with my volt meter in case it happens again so I can see what it looks like when it fails. If something else in the ecm is shorting I should see stray voltage coming out. Of course I won't be able to do anything about that.

  5. #5
    surferd15's Avatar
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    Hey man do you have any more information on this? I am also trying to figure out why these ECMs fail..Maybe its heat? I am going to relocate mine. I bought a ski and everything was going fine until we rode it for 2 days then I got the 25 code..I replaced the knock sensor and no go...same issue. I removed the knock sensor (still had it connected) and ran it on a hose, same code. So ECM is bad, but when I replace it I don't want it to happen again...

  6. #6
    supermac's Avatar
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    Quote Originally Posted by surferd15 View Post
    Hey man do you have any more information on this? I am also trying to figure out why these ECMs fail..Maybe its heat? I am going to relocate mine. I bought a ski and everything was going fine until we rode it for 2 days then I got the 25 code..I replaced the knock sensor and no go...same issue. I removed the knock sensor (still had it connected) and ran it on a hose, same code. So ECM is bad, but when I replace it I don't want it to happen again...
    they fail from corrosion caused by failing potting compound.
    The knock sensor circuit typically fails first as it is the most sensitive to signal levels.

    corrosion starts to short circuit the signals and eventually the noise gets to a level that trips a code.

  7. #7
    They all fail. I not sure it has anything to do with Corrosion. Because I have sold ecm to fresh water skis with 10 hrs and to salt water skis with 1800 hrs. I think they just go bad from age. they seam to last about 8 years. and with them always having electric running thru them 24 hrs a day 365 days a year at 8 years that's 70,080 HRS on these ECM before they Fail.......

  8. #8
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    Quote Originally Posted by skidr View Post
    They all fail. I not sure it has anything to do with Corrosion. Because I have sold ecm to fresh water skis with 10 hrs and to salt water skis with 1800 hrs. I think they just go bad from age. they seam to last about 8 years. and with them always having electric running thru them 24 hrs a day 365 days a year at 8 years that's 70,080 HRS on these ECM before they Fail.......
    Whats the price on a replacement ecu?

  9. #9
    AWA MEMBER
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    1k for newer models and 2003 are the least expensive

  10. #10
    AWA MEMBER
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    Quote Originally Posted by tyranny View Post
    The harness seems fine, IE no obvious wears or knicks. I want to start up with my voltmeter probing the line. I should see a low range of ac voltage starting at idle and increasing as the rpms go up. If I see a clean signal then I assume its the ECM. From there I hope the ECM is just over sensitive. If it triggers consistently at a higher voltage I can either isolate the knock sensor or come up with something to simulate an acceptable voltage while I ride. I could care less about knock at this point. I just don't want to have to part out the ski. If anyone has been down this path before though let me know if I'm wasting my time.


    I would NOT bypass the knock sensor......That is a critical sensor for Boosted applications and is always keeping your Honda motor out of trouble.......lose that and you may lose alot more......just my 2 cents


    what if you get less than 91 octane from a station or for some reason while running the motor modified with a Macs boost or other device....it runs lean....you have no safety to cut back the timing thus you will get detonation and a wasted motor. My advise to you is to think about what the ski is worth to you and is it worth dropping 1k on a ecu......it might be solid for awhile after that

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