What can cause an ECU failure?

Discussion in 'Mechanics Garage' started by philinnc, Jan 11, 2022.

  1. Terry Smith

    Terry Smith Member

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    Like Squirrel says, Grum is The Man for electrical advice. However, maybe you don't have an electrical issue. IIRC you indicated that the bike would fire when you used starting fluid, but never on its own? Have you verified that the injectors are, in fact, doing some injecting? Maybe there is some fuel supply issue (e.g. blocked pump filter) that is causing grief, or the injectors themselves are gummed shut.
     
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  2. squirrelman

    squirrelman Member

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    following on from terry's idea................crank for awhile then pull a sparkplug. if it's dry, you're not injecting fuel, and you have a FI problem, not ecu.
     
  3. philinnc

    philinnc New Member

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    FWIW--I'm back to the steady FI light with the jumper in place, side stand down, key on, RUN position.
     
  4. Grum

    Grum New Member

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    Ok you now appear to be back to a normal situation regards the Fi Light = Goes OUT after Fuel Prime.

    You could try just unplugging the MAP Sensor then attempt to start your bike, that should induce an active fault and the Fi Light should Flash a Code 1. Switch off, plug the MAP Sensor back in, retry a start and the fault code should not be present, however, it will have stored this into memory.
    If you did have a genuine MAP sensor Fault Code then check the electrical connector to the MAP sensor and make sure the vacuum hose to it is connected and not cracked, have a good check that all vaccume hoses are in good shape. Note the MAP sensor can be swapped with the BARO Sensor for fault finding.

    So it might be that your original problem with the Fi Light being fully on could have been an issue with the memory clearing process!

    Now back to why your bike won't start - as previously mentioned you might need to confirm the operation of the Injectors. Having been stored for so long and not run they may have gummed up.
     
    Last edited: Jan 13, 2022 at 7:53 PM
  5. Grum

    Grum New Member

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    Good news - Remove the Jumper!.
    Manual States with the jumper fitted "If the ECM has no diagnosis memory data the MIL light will illuminate when you turn the ignition switch on"

    You have cleared the memory so now when the jumper is fitted the light being on is Normal!
     
    Last edited: Jan 13, 2022 at 4:46 PM
  6. philinnc

    philinnc New Member

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    I did the MAP unplug and replug--everything happened as you said it would. And now, after clearing the memory, the FI light blinks as it should. I love it when things happen as they should. Now if only it would start!
     
  7. philinnc

    philinnc New Member

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    Am I correct that the FI malfunction system only looks upstream? That is--it monitors sensors and such that impact the operation of the ECM. There is nothing that monitors the operation of the ECM itself.

    So, while everything before the ECM is working OK, I don't know if the ECM itself and anything downstream (the fuel injectors) are OK. I'll remove an injector and check its cleanliness.

    Yep, a voyage of discovery!
     
  8. Grum

    Grum New Member

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    At power On the ECM does its own self check - Fuel Prime and the Fi light going out will mean alls well with the ECM and sensors, at that stage.
    Generally speaking, and as complex as it is, the least problem causing item with EFI is the ECM itself, it's everything hanging off the ECM that causes issues! Power, R/R, bad wiring, poor grounds, faulty sensors, fuel system/delivery, spark plugs etc. are the most common issues.

    You mentioned your bike "laid idle for several years" that doesn't sit well for the Injectors. The ECM can only detect an open or short circuit for the wiring or the Injector itself, it can't detect wether it's actually injecting fuel.
    As Squirrelman mentioned, if after cranking you check a plug and its dry there's a good chance the injectors are not operating. It would be worth removing them and have them professionally cleaned and flow checked.

    With the new fuel pump you've fitted. Have you at least done the Fuel Flow test page 5-57 of the Service Manual? Would also be good to know you have good Fuel Pressure as well to confirm fuel delivery is correct. Best get the injectors checked out first I suppose!

    Good Luck and keep us posted.
     
    Last edited: Jan 15, 2022 at 8:46 PM
  9. raYzerman

    raYzerman Member

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    I'd bite the bullet and go get the injectors cleaned and a flow test... $100 well spent for peace of mind and eliminating them from the equation.
     
  10. philinnc

    philinnc New Member

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    Rather than try to disassemble everything to get to the injectors, I thought I'd follow the wires from the ECM to insure wire condition and continuity. On the wiring diagram there seems to be a connector--pointed to in the attached file. Does anyone know where it is located?

    Never a dull moment--and 6 inches of Mother Nature's finest fell yesterday!
     

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  11. Grum

    Grum New Member

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    You do have the Service Manual I take it?
    I don't have a 5th gen but according to the Service Manual the Throttle Body sub harness Gray 10p connector appears to sit above the left side radiator front upper corner!
     

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  12. squirrelman

    squirrelman Member

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    crikey ! it would be madness not to have the manual. :eek:
     
  13. philinnc

    philinnc New Member

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    Yes, I have the manual, but missed that description. Ironically I just put he left side fairing back on1 I did see that connector but didn't realize what it was.

    It's easy to remove so I'll take a look at it.
     
  14. philinnc

    philinnc New Member

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    I am planning on establishing continuity from the ECM to that connector. Is it hopeful to assume that voltage will appear at an injector terminal when the bike is started? If so then I would be able to confirm that the ECM is sending voltage to the injectors, thus ruling out a faulty ECM.
     
  15. raYzerman

    raYzerman Member

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    Couldn't you just check the voltage output at the injector connector itself? You're just resisting pulling the airbox off, you should be in there already, checking MAP sensor and hoses, etc........
     
  16. philinnc

    philinnc New Member

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    I would like to do that, but one of the screws holding an air funnel refuses to give way.

    The MAP sensor give the correct error code when unplugged, that disappears upon re-connecting. Hoses look fine.
     
  17. philinnc

    philinnc New Member

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    A concern that I have is whether voltage at the injector tells me anything. My Aprilia has a similar non-spraying issue--and it has voltage at the injectors. Apparently its ECU shorts the injector allowing it to spray. The Honda's explanation indicated (if I read it correctly) is the opposite. (FWIW--the Aprilia forum also said that the pulsing of the ECU is too fast for a voltmeter to register.)
     
  18. Grum

    Grum New Member

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    Solid 12v should be on the Black/White wire to all 4 injectors. The ECM controls the Ground side of the Injector.
    Doubt that your digital voltmeter will be capable of measuring the injector pulses.
    If you have wiring continuity, confirmed the 12v to the injectors on the Black/white wire and each injector measures the same resistance then there's not much more you can do.
    The ECM is detecting the impedance of each injector circuit, a failure of any injector circuit = Dead Engine and a Fault Code flashing for the faulty injector circuit. You are not seeing a fault code for any injector. The ECM can't detect if the injector is gummed up.
     
    Last edited: Jan 18, 2022 at 2:22 PM
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  19. philinnc

    philinnc New Member

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    Oddly, this is like deja vu--my Aprilia (V-twin, 2008) has exhibited the same issue--good spark but no spray. (It also sat idle during my chemotherapy.) Its injectors have battery voltage and have been cleaned--but do not spray via the ECU. That seems to leave the ECU. Sadly, a used Aprilia ECU has not been as easy to find as one was for the Honda--which is on its way. Stay tuned for an update!
     
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