Hello everybody, new member, this is my first post. I'm very mechanically inclined, but I have very little experience with motorcycles, most of it is from working on this bike.

I have a 2003 Fatboy I'm trying to diagnose. Need help as to where to go next. This bike is heavily modified. Woods cams, big bore kit, posted heads, it's tuned directly to the computer. (Had issues with the piggy back).

First, the problem(s): about a year ago I started having this issue. I have no speedo, but also the bike won't idle at almost every stop I come to. Either hit the kill switch or crack the throttle to keep it running at a stop.

What I've done: I've flushed all the oil shavings from the tranny, I'm on the 4th flush (I read that the metal shavings can interfere with the signal and seen that in the past...with other stuff). I've replaced the speed sensor, with a factory harley sensor, no change. I OHMed the wires from the speed sensor to the speedo, .1 or .2 every time. I tried a different, known good speedo, no change.

I'm assuming I have a wiring problem somewhere, just not sure where to get the right diagram.

I've also read about the fuel lines inside the tank cracking from E10/E15 and causing the same issue. I was thinking the speedo is related as the symptoms started at the same time. The lines have been replaced already, just not recently (7-8 years ago) Any ideas, or direction would be extremely helpful.

 

One of the things the ecm needs to see is vehicle speed to control iac motor.

 

I have you tried clean the sensor? On top of tranny, if I remember right. Never had an issue, but people say to clean it if speedomtoter gets funny.. Can try by just wiping it off. If not, can look up what it;s output is supposed to be, so you can test it.

 

Ive been reading that Lone Wolf. Also read that the ecm shorts out and can cause this same issue, for the same reason.

I did try cleaning it when the problem started, Rounders. Also between flushes, it still needed to be cleaned. Last time I took it out it was still clean after the fourth flush...

The CAN bus is working because everything else on my speedo works...may be ordering an ecm soon.

Thanks for the tidbits!!

 

Do 2003 have canbus? I thought that was newer bikes with BCMs. Probably showing how dumb I am. Might have to check output from speed sensor, Maybe code would tell you if bad??

How about codes? Have you gone in through dash to look at them? Hold trip button in, turn bike on, release.

 

Ooooops

 

Rounders, from what I looked up, I may be wrong 2003 Electrical diag book says it has bcm, ecm, etc. However the wiring is wrong on every single page, so maybe in not looking at the right stuff. Ooops, 2013, that would be why nothing is right hahaha

On another note, I have no ability to grab codes from the speedo/odo...

If the ecm needs VSS data, how would it comm with the ecm without even a single band? I may have to grab a 3 pin from work and test it out.

 

Do you have stock ECM? It needs to the kill switch on. hold trip button in, turn bike on, release trip button.

 

Ive tried it multiple times, not sure I had the switch on.

Also tried jumping the diagnostic port, nothing.

 

That could be a hint. But I would make sure doing right. The kill switch must be on.