ECM Issue?

Discussion in 'Dyna Models' started by dmz1965, Aug 30, 2010.

  1. dmz1965

    dmz1965 Member

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    Did a search regarding the loss of tac and speedo while riding and returned the thread regarding some issues with the ECM that may be the cause. The other day my FXDL began to miss and backfire at about 70 MHP (no "check engine" light illuminated), I slowed down and was going to pull off the road to see if I could figure it out and the bike came out of it and has not done it again in about 200 miles of riding. I changed the plugs and wires the other day since I am hitting the road over labor day weekend for a 1300 mile trip; my question is with the loss of the tac and speedo (at times) and now the backfiring/missing could both be attributed to the ECM?
     
  2. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Maybe, but lots of other stuff to check out first. Start here:

    04-07 HD DTC Codes and Activation - Harley Davidson Community

    TQ
     
  3. Hoople

    Hoople Account Removed

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    I am in agreement with TQ ,, Anything is possible,, but is it likely? I would say no. Don't go by the check engine light to know if there are any stored codes. Check it using your year flowchart and side-button.
     
  4. dmz1965

    dmz1965 Member

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    Just checked codes, none stored.
     
  5. Hoople

    Hoople Account Removed

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    I was really hoping for an intermittent crank sensor code. That would have explained at least the intermittent tach and miss-fire/backfire.

    So you have no codes, none. And your dealing with just (4) problems.
    Missing Tach
    Missing Speedo
    Engine miss-fire
    Engine Backfiring.

    Are there any more symptoms? Do they happen in a group or can you have missing tach/speedo and the bike runs fine with No hint of miss-fire.
     
  6. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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  7. eleft36

    eleft36 Junior Member

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  8. dmz1965

    dmz1965 Member

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    No additional symptoms; lose the the tac, speedo and auto cancel on the turn signals but otherwise all is fine. When the backfiring was going on all guages were working normal; next will be the checks TQ recommended.
     
  9. Hoople

    Hoople Account Removed

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    No additional symptoms? You just named one which was no auto cancel on turn signals. That supports a no Vss signal is present and the importance of that is you now have not one but TWO sub-systems missing a Vss signal. The TSM AND Speedo. But somehow the ECM is seeing that Vss signal because it fails to log a DTC.

    It's almost like the Vss signal is on the Bus and the ECM is seeing it,, but it's not making it to the Speedo or TSM modules. Since it is intermittent, just checking the Vss output signal won't tell you much. It's not cheap ($50) but maybe throw a new Vss pickup at it just to see where it takes you. I would also do a "plug & reseat" of the large ECM connector,, a Plug and reseat of the TSM & Speedo module cables also.
    The Vss signal is a shared signal transmitted on the 2 wire Bus. A poor connection on the module could do it.

    Do the checks that TQ suggested first. If you draw dead, plug & reseat the 3 large connectors. It's an '06 bike and those connectors could have some oxidation on them.

    Just thought of something. If you look at the possible DTC codes for your bike, you only have two DTC's for a Vss issue. They are P0501 & P0502. Both of those codes are ONLY for an Open or Shorted Vss sensor. There is no code that I can find for an intermittent or missing Vss signal. Those two codes are almost useless in a case of an "intermittent signal" such as yours.

    That places a LOT more weight on the Vss sensor being bad. I would look REAL close at that sensor for starters. You can check the output with a meter but I have this feeling you have a marginal signal.

    That may at least fix the speedo & turn signal issue.

    That missing tach signal has me puzzled since you did not post a crank signal DTC.
     
    Last edited by a moderator: Aug 31, 2010
  10. cdn-bigfoot

    cdn-bigfoot Junior Member

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    Lean angle sensor malfunction will cause engine to cut out and give you some signal auto cancel issues. Worth checking it out.