Bike died while riding - zener diode? -
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post #1 of 2 (permalink) Old 08-14-2018, 03:23 AM Thread Starter
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Bike died while riding - zener diode?

Hi all,

Background: CBR 600RR 2004 (HISS)

Bike died while riding. Had the ignition and ECU swapped out with test kit - bike fired up. Brand new yasua battery also installed.

Swapped back in original ignition and ECU, checked voltage coming from ignition pink wire to ECU - 12v.

Had the zener diode replaced, now the current voltage reads exactly at 9v, and the battery is resting at 12.1v

I recall reading somewhere the voltage from ignition to ECU should actually be 9.3v, rather than 9v - is this true? could it be a case of just needing to charge the battery more, or is the ECU at fault? (Find it hard to accept, as bike died while riding, dont see how the ECU can just fail on a ride).

Thank you all
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post #2 of 2 (permalink) Old 08-15-2018, 07:12 AM
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Don't replace 2 things at the same time. You can't tell which one is bad by doing this. The ECU can go bad, just the part that controls the fuel pump. It's in the manual on how to test this to see. If the ECM doesn't get 9v from the ignition it won't turn on the ground to trigger the fuel pump relay to send 12v to the fuel pump. You have the "test" kit and it corrected the problem so now swap out and see which one has failed.
The ECU has a range to work the relay, battery being at 12.1 won't cause it to not work, have had the fuel pump turn on but not enough power to turn over the bike, bump start it and it works fine. It was hondas way of a safety device to prevent hot wiring. You couldn't bypass the zener and get it to work unless you know the wiring.

Side note what value did you get for your zener diode or did you replace with an ignition with the correct diode already in there?
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