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Discussion Starter · #1 ·
Years ago, the FI light came on while I was riding my 2002 Blackbird and when it did the temperature of the bike immediately went up at least 15 degrees and the throttle response got sluggish. If I turned the bike off and restarted it, the problem would go away for awhile and then appear again. I never knew when it would appear and couldn't figure out what was wrong. The ECM was throwing a knock sensor code. I erased the code in the ECM, but that only helped for awhile. I ended up buying a used ECM on eBay to replace it. Everything was fine until...

Here I am several years later and the FI light came on again with the same temperature increase and sluggish throttle response. I cleared the code and then the bike sat for quite awhile before I could get around to trying to address the problem.

Here is what I have determined after getting the bike running again. First of all, the knock sensor is rarely at fault. It is doing its job. I believe the ECM was throwing a code because 1) I was consistently using a poor quality low grade fuel and 2) was consistently operating the bike at too low of RPM.

I have been riding the bike for several weeks now with 93 octane fuel and have also put some Lucas octane booster in each tank of gas - quite a bit of it in the first tank I rode on. The bike is running much smoother and there have been zero problems with it. Instead of riding around at 3.5-4k RPM and shifting at 4K RPM, I run the bike between 4.5-5K RPM and shift at 5K RPM now. The bike does feel busier at the higher RPM's and uses more fuel, but I think it's the key to keeping the bike happy for general cruising around.

That's my 2 cents. If anyone is having similar problems with the FI light and code, this could be the problem/solution.
 

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Sunnybird, you have a 2002 model, so presumably this is a digital dash unit. The knock sensor or code 25 problem usually occurs on analog dash models for some reason.
Some riders report no running issues at all, some do.
As you say, the knock sensor is never the fault.
To my knowledge, the triggers are:
1. Loose ECU, allowing it to bounce around
2. Wiring fault AKA the loom fix.
3. Bad ECU.

In your case I would review the loom fix.
 

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Discussion Starter · #4 ·
Silly question but how do you clear ECM codes?
It's not a silly question. I'm not sure where I got the directions, but I couldn't find them in the shop manual. I could scan and upload the instructions in .pdf if you need. I would think that info would be listed somewhere else on this site, though. Let me know.
Sunnybird, you have a 2002 model, so presumably this is a digital dash unit. The knock sensor or code 25 problem usually occurs on analog dash models for some reason.
Some riders report no running issues at all, some do.
As you say, the knock sensor is never the fault.
To my knowledge, the triggers are:
1. Loose ECU, allowing it to bounce around
2. Wiring fault AKA the loom fix.
3. Bad ECU.

In your case I would review the loom fix.
Yes, too many owners replace the knock sensor and really lots of other things that aren't at fault when they get a knock sensor code. It's definitely been the knock sensor code for me and I know it has to be a fuel injection/ignition system problem if the FI warning light is illuminated while the bike is running. ECM is not loose and is nicely padded. Not sure the loom fix applies to 2002. Would seem odd that I could go years without the problem and it would be a loose ECM or the loom. Could be a bad ECM. Again. But, the problem has gone (for now?) with the changes outlined.

Thank you for your insight and willingness to help. Always appreciated.
 

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The loom fix issue can appear at any time. This particular hidden junction block can corrode over time and at some point the ECU becomes unhappy with the signal it receives and boom.
 
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