BAD ECU? PLEASE HELP
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Thread: BAD ECU? PLEASE HELP

  1. #1
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    Default BAD ECU? PLEASE HELP

    I have this crazy problem. My Power Commander display is reading a transient drop to 0 RPM. The bike will idle and low speed cruise okay, but when I open the throttle, the 0 RPM condition becomes more frequent and signal to the injectors doesn't occur so the bike sputters like crazy. I've swapped the PCV and that isn't it. I replaced the TP sensor and it didn't fix it. Also, the guys from Dyno-Jet connected remotely and couldn't figure it out.

    Now, I investigated the CKP sensor by hooking up an oscilloscope. It shows a typical waveform for a VR sensor but with a flat spot I presume to be the missing tooth area of the tooth wheel. What it looks like is the ECU is failing to properly calculate the missing tooth section of the tooth wheel and is instead coming up with zero RPM and that's what the PCV is seeing. Does this sound plausible? I just can't figure out why the ECU seems to be putting out this random 0 RPM condition. Tomorrow I will scope the wires at the ECU I guess. Is there anything other than a bad ECU that could cause this?

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  3. #2
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    Quote Originally Posted by Syler View Post
    What it looks like is the ECU is failing to properly calculate the missing tooth section of the tooth wheel and is instead coming up with zero RPM and that's what the PCV is seeing. Does this sound plausible?
    I'm no expert by far but I would say that absolutely sounds plausible.

    The ECU is looking for the high low signals from the reluctor wheel and when it doesn't read it as expected will behave erratically. I'm guessing it will try to respond via closed loop control but when the ecu "realizes" the issue is out of control, will default to a standard program control.

    So every revolution you get a good closed loop response to a bad open loop response to a standard preloaded response back to a good closed loop response. The faster you go, the more cycles the ECU expects to see, and doesn't, which makes the issue worse.

    It very likely isn't trying to calculate around that flat spot you mentioned.
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  4. #3
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    The missing tooth section is supposed to inform the ECU of position. It seems like instead of the proper calculation, the ECU spits out a 0 RPM state.
    Last edited by Syler; 1 Week Ago at 01:45 PM.

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  6. #4
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    Well the CKP sensor is good so it looks like this thing is off to the dealer for a scan.

  7. #5
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    OP's profile shows he is in North America so the comment about the ECU running in closed loop does not apply at all.

    Try removing all the dynojet hardware (completely) and see how the bike runs only on the OEM ECU.

    Most Suzuki dealerships are going to charge a fortune to diagnose the issue and likely will have no real answer to the problem after emptying your wallet.

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