MIL Light

Discussion in 'Maintenance' started by t0m541, Nov 23, 2013.

  1. t0m541

    t0m541 Senior Member

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    I recently fitted an aftermarket speedo and riding to work this morning the MIL light came on.
    The reason it is on is because I have the speedo sensor disconnected as the new speedo has its own sensor.
    I'm not too fussed about the light being on, although I would like to know if the ECU will go into limp mode or similar ?
    Thanks in advance for your answers :)
     
  2. SpeedoX

    SpeedoX Active Member

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    Guess you have answered your own question here pal!
     
  3. Nutty Tart

    Nutty Tart Well-Known Member

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    Arthur might be able to tell you what you need to know when he gets on

    He is the font of all knowledge Blade wise
     
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  4. arthurbikemad

    arthurbikemad A very helpful Gent

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    Ha!

    Ok so I'd guess this, disconnecting the speed sensor will no longer send the signal to the ECU I think you will find the HESD uses the speed and TPS to function. :)
     
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  5. arthurbikemad

    arthurbikemad A very helpful Gent

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  6. t0m541

    t0m541 Senior Member

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    Ok so the steering damper wouldn't work....so do you think it would default to full damping or zero damping Arthur ??
    Interestingly though...tonight on the ride home, which is the same route as this morning, there was no sign of the MIL light, no matter how hard I rode..
     
  7. arthurbikemad

    arthurbikemad A very helpful Gent

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    It would be zero mate, weird if not on again, I know it depends on throttle position and speed.

    You would be surprised how little it does, you can test it by, stand down, engage first gear, open throttle fully, switch on, move bars left and right, repeat often, feel change until returns to normal.

    There is no limp mode, check MIL light error code if happens again.
     
  8. t0m541

    t0m541 Senior Member

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    I'll give that a go tomorrow...as I said the ride home was very similar to the ride in, various amounts of throttle, up and down through the box at various throttle settings.
    The only thing I changed today was the high speed warning and rev warning lights on the clock, the speed was set at 40mph and the revs at 7k...I wouldn't have thought they would have any effect on engine management...

    It's a shame there isn't a schematic of the Honda dash that shows how it's circuited up internally...
     
  9. arthurbikemad

    arthurbikemad A very helpful Gent

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    The test will only test the function of the damper, your right about the flow chart, Honda have a MASSIVE technical on just the HESD as you'd expect. I'm not looking at a diagram but even with one it would be hard to say if the ECU takes data directly or from the dash? As I say I did read some of the HESD technical some years back, it was about twenty pages long!

    Mate I could be up the garden path, but I know for sure the HESD needs speed data, did you disconnect the speed sensor from the gearbox?
     
    #9 arthurbikemad, Nov 23, 2013
    Last edited: Nov 23, 2013
  10. arthurbikemad

    arthurbikemad A very helpful Gent

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    Oh I should say reason I say about the HEDS is that's properly what the MIL is for, and the failure would be no speed input. Related to the clocks.
     
  11. t0m541

    t0m541 Senior Member

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    I think you're right, the ECU/HESD takes the data from the speed sensor directly, (3 wires on sensor), 1 feeds the dash, 1 the ECU and the 3rd is the 5v control voltage, so obviously having the sensor unplugged confuses the hell out of the ECU....I would imaging there is resistance sensing in the HESD unit that feeds the ECU with steering input so it can work out the damping rates for given RPM/MPH/TPS.

    Without this data it throws the MIL light to make the rider stop as the software doesn't have the capacity to allow for the bike to be ridden by some crazy who has decided to disconnect stuff :O
     
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  12. arthurbikemad

    arthurbikemad A very helpful Gent

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    Yes like I say the MIL will be for the HESD, it's not that cleaver to have different forces that I know, think it's just dampen or not, also it's flawed as it only functions with larger throttle openings so small amount of throttle and you have no damper, saying that Honda don't give much away about the function so I'm not 100% but run the test and you will get an idea of the amount of force it applies. I doubt the loss of the MPH will chuck up a MIL but the failure of the HESD defiantly does. :)
     
  13. t0m541

    t0m541 Senior Member

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    I'm guessing that the only real way to circumvent the safety buffers built into the loop in the ECU would be a custom firmware lashed into another ECU then swapped over, if re-writing the ECU is even possible on a Honda, I don't supposed their coding is that easy to crack, being one of the more technical manufacturers
     
  14. arthurbikemad

    arthurbikemad A very helpful Gent

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    I have never know anyone flash or read the raw code from a Honda ECU, it's locked down afaik.

    I'm surprised you have an error if you have left the gearbox sensor connected and just changed the dash, guess the dash has a mag pickup on the wheel? Some state they will not accept an input from the gearbox sensor like the microtech but it does work in practise. The microtech is high impedance so the ECU does not know it's there.
     
  15. t0m541

    t0m541 Senior Member

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    As far as the ECU code...yes I agree about it being locked out, maybe only way to do it is with a Honda dealers piece of kit, even then it's not the sort of thing ypu would find at the local showroom....maybe the MotoGP boys lol

    The G/Box sensor I disconnected, the Koso clock has an active sensor that picks up from the rear sprocket bolts...it's nice to have an accurate speedo reading for a change.

    I'm not sure whether it's placebo effect but throttle response seems crisper now in every gear..I realise that common theory is that the max speed restriction on all sports bikes is achieved through RPM/TP/Gear Selected algorythm
     
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  16. arthurbikemad

    arthurbikemad A very helpful Gent

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    Yes known as 3d mapping, reconnect the GB sensor and all will be well I'm sure :)
     
  17. t0m541

    t0m541 Senior Member

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    I'm assuming you have had one of these out on the bench ??
    So at a guess it's a pinion wheel driven from the final output bevel of the gearbox, pinion wheel drives either wheel with paddles that set up on/off pulses that are picked up by active magnetic sensor that the ECU/Dash reads and converts...badly...into a MPH readout..

    Just plugging in a sensor wouldn't get around the error code and there wouldn't be any pulses read...sorry just bouncing ideas around...unless there was a way of false pulsing on the return path..
     
  18. t0m541

    t0m541 Senior Member

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    Just seen a picture on eBay...it's a bit like a crank/cam shaft position sensor...
     
  19. Skippy79

    Skippy79 Active Member

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    never seen a Mother In Law light on my bike :D :D
     
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