ECM not pulling Yellow/Blue wire low to near zero volts
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Thread: ECM not pulling Yellow/Blue wire low to near zero volts

  1. #1
    Baby Twin apex69's Avatar
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    ECM not pulling Yellow/Blue wire low to near zero volts

    This on my 2000 TL1000R w/20k miles. Bought new in 2000. Replaced the fuel pump three years ago, the motor brushes on the factory pump had disintegrated.

    Following some great threads, analytics all around ... I created a troubleshooting punch list from those threads and went at it.

    Wondering if there is a short answer to this that perhaps someone else had experienced.
    ECM not pulling Yellow/Blue wire low to near zero volts
    Is this the result of a known issue that develops over time?


    Key on, kill switch on, stays at 12.9v
    Key on, turn kill switch off, goes to 0.0v
    Key off, measures 0.0v

    Followed all the checks as listed by Six5 among others, thank you, including:
    - removing and inspected the fuse/relay block from the side of the intake duct to look for/at corrosion/connections - good
    - removed and inspected starter relay block to look for/at corrosion/connections - good
    - tested the FPR off the bike - good
    - TOS checked
    - wires checked for continuity, fuse / FP relay / starter relay

    One last observation ... I noticed a few months ago that the 3 seconds for pump prime became intermittent that is, at random times after the 3 seconds passed, with key on, the pump would keep running and not shut off. This was when the bike was cold, or hot w/o an attempt to start it. Again, sometimes it would work normally getting the 3 second prime then the pump would shut off, other times it would just keep pumping w/o shutting off. Pump works fine but not when connected through the factory connections.

    I told myself I was going to make this a simple thread lol. Ask me what time it is ... and I'll build you a clock.

    Not a head banger by any means. Thanks

  2. #2
    MotoGP Pit Boss The Ring-In's Avatar
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    youve told us the observations but what is the problem you are dealing with


    cheers stu

    Naked TLS 97 , D port heads, TRE, Carrozzaria gold wheels, GSXR750 triples and forks, R1 calipers, Ti Force titanium exhaust system, welded clutch centre, ring-in CCC, polished pressure plate, 999 ducati radiator, custom handlebar fairing, polished ali screen, TLR clocks, Van reservoirs, TLR swingarm, TLR Ohlins rear shock, Norton Commando handlebars on 65mm risers, extra heavy polished billet brass bar-ends, custom shaped seat pad, billet levers and pegs, stainless brake lines, modified airbox, PC11 ,undertail, hugger, clear taillight lens, hidden LED number plate lights, Personal number plate (97TLS),SV coils, ring-in pushrod seal saver.

  3. #3
    AMA Pit Boss Six5's Avatar
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    Quote Originally Posted by apex69 View Post
    T.....
    ECM not pulling Yellow/Blue wire low to near zero volts
    Is this the result of a known issue that develops over time?

    ......
    One last observation ... I noticed a few months ago that the 3 seconds for pump prime became intermittent that is, at random times after the 3 seconds passed, with key on, the pump would keep running and not shut off. This was when the bike was cold, or hot w/o an attempt to start it. Again, sometimes it would work normally getting the 3 second prime then the pump would shut off, other times it would just keep pumping w/o shutting off. Pump works fine but not when connected through the factory connections.

    ....
    A nonfunctional Yellow/blue control line is not something that fails with time, per se. However, some ECMs have been know to fail in that manner. The drive transistor inside the ECM stops working and is no longer able to pull the voltage low on that terminal to turn on the FP relay. I have an ECM like that in my shed right now.

    Still, before we jump to any conclusions, there are elements in the loom that could cause a similar condition, so it not actually be an ECM failure. However, if any of these other issues were the cause of the problem, an error code should be generated, and the classic "FI" icon would be displayed in the LCD window. If no error code appears after key on or after cranking the engine over for five seconds, the chances are good that the ECM's fuel pump control output has failed.

    The intermittent fuel pump activity you have experienced with just the key on could be due to an intermittent connection in a loom wire or a switch. Or maybe those are the symptoms the pump control circuit in the ECM actually failing. IDK. It is difficult to say emphatically without spending some time with it.

    See page 4-27 in the manual for the conditions that can stop the fuel pump enable, as well as the associated test sections for the specifics.

    TLR 4-27_highlighted by Tony Six5, on Flickr


    If you find that the systems in question are functioning properly and not preventing the ECM from enabling the FP relay, then all is not lost. Even with this sort of ECM failure, the fuel/injector system can be made to function, but it loses the ability to shut off in the event of a tip over.

    Have a closer look and let us know what you find.
    January 2012 TLOTM & BBOTM


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  5. #4
    Adrenaline Junky CrashB's Avatar
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    Quote Originally Posted by Six5 View Post
    If no error code appears after key on or after cranking the engine over for five seconds, the chances are good that the ECM's fuel pump control output has failed.

    The intermittent fuel pump activity you have experienced with just the key on could be due to an intermittent connection in a loom wire or a switch.
    Once (if) you get to this stage get a multimeter and start from the fusebox and work your way along the loom. Check the input into fuse 5 (light brown) with the ignition on, then check the output (dark brown). If you get readings on both of these then check the orange/blue going into the fuel pump relay. If you have a reading there then try the yellow/red wire leaving the fuel pump relay, then check were it goes into the fuel pump. By this time you should have located the drop where there's a break in the circuit.

    ECM not pulling Yellow/Blue wire low to near zero volts-fuel-system.png

    This is a TLS diagram, but the colours/locations are all the same minus the two extra TLR injectors

    If you have confirmed the ecu is living (as Six5 outlined above) and you have found where the break in the circuit is then use a length of wire with a dab of solder to stiffen each end to bridge out that section. If you do that and everything works then you have found your culprit.

    Report back.


    '97 TL1000S Streetfighter 'Evil Twin' - Full colour wiring diagrams - click here for UK TLS - click here for US TLS - click here for UK TLR - click here for US TLR

  6. #5
    Baby Twin apex69's Avatar
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    Quote Originally Posted by The Ring-In View Post
    youve told us the observations but what is the problem you are dealing with
    imagine that lol ... thank you,

    - Do not hear the relay click as before (as mentioned, works bench tested)
    - Fuel pump does not come on
    - F1 shows on display
    - Dealer mode shows c41

  7. #6
    Baby Twin apex69's Avatar
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    Six5, as mentioned to The Ring-In, there are error codes.

    Thought it odd the pump always worked, and again, the 3 second prime shut off became intermittent.
    Thank you for page 4-27 ... will go through that diagnostic.

  8. #7
    Baby Twin apex69's Avatar
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    Quote Originally Posted by CrashB View Post
    If you have confirmed the ecu is living (as Six5 outlined above) and you have found where the break in the circuit is then use a length of wire with a dab of solder to stiffen each end to bridge out that section. If you do that and everything works then you have found your culprit.

    Report back.

    Thank you for the diagram and the additional input. Will work through each of these items and "report back"

  9. #8
    AMA Pit Boss Six5's Avatar
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    Quote Originally Posted by apex69 View Post
    ....
    - Do not hear the relay click as before (as mentioned, works bench tested)
    - Fuel pump does not come on
    - F1 shows on display
    - Dealer mode shows c41
    The c41 error code provides further confirmation that the FP control line is failing (has failed).
    I say this because you previously stated:
    The fuel pump works on the bench.
    The FP relay works on the bench.
    The Orange/Blu wire has 12V on it (implied from your tests up to this point).

    If no other error codes are displayed, then that nearly insures that no other system is preventing the ECM from commanding the FP to run. And that agrees with what you are seeing.

    Notice in CrashB's fuel pump diagram: The Yellow/Blu wire is the control line from the ECM. It should activate the FP relay, which then connects the Orange/Blu wire to the Yellow/Red wire - providing power to the fuel pump and injectors.

    The ECM also monitors the Yellow/Red wire to 'know' if the system is functioning. Since it sees no voltage on the Yel/Red wire, it generates the c41 error. So then, the ECM is issuing the fuel pump command internally, and looking for the result, but it doesn't know that the output drive transistor has died (or there is a break in the Yellow/Blu wire).

    Still, verify the continuity of the circuits with Crash's suggestions and let us know what you find.
    January 2012 TLOTM & BBOTM


  10. #9
    Baby Twin fubar's Avatar
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    I may have the same issue on my '97 S. I'm going to re-check everything this evening. Is there a way to repair the output drive transistor?

  11. #10
    GP Champ rxf610's Avatar
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    Quote Originally Posted by fubar View Post
    I may have the same issue on my '97 S. I'm going to re-check everything this evening. Is there a way to repair the output drive transistor?
    You HIGHLY LIKELY don't...

    I have NEVER seen/heard an S transistor in the ECU go. I have heard of several R's... and my personal R ECU was also a victim...

    Start a new thread. We can fix it...

    Apex69,

    Pierce the Yellow/Blue wire with a needle.

    Then short the needle to ground... right there on the subframe is a good place...

    The pump should now RUN and ALWAYS RUN with key on kill in run position... (a la... no 3 second prime, just go go go).

    The bike SHOULD start and run (and keep that c41 code, but run nonetheless).

    Unfortunately the only "fix" is a new ECU. I was going to make a "fix" but it just was too cost prohibitive and complicated.
    ... listen to Six5 ...

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