I have the rapid flash, but it also turned on the security light. I checked codes & one is the turn signal module, so I figured that was causing it. ITS A CVO & already had LED rear lights from factory, but regular bulbs for front signals. Doesn't make much sense but not sure where to go from here. I cleared code, turn signals start normal, then go to rapid flash.
If it has a BCM/can bus, you have to set the 4-way flashers on for like 2-4 minutes for the system to learn the new load.
I upgraded all four incandescent turn signals to LEDs on the 22 and ran the hazards like that. Instructions with CD stuff said flip the run switch on, turn on hazards flip run switch off (hazards keep flashing). Waited 3 minutes, flipped the run switch back on (because apparently hazards won't turn back off otherwise) and it was fine, never had rapid flash.
I also don't get codes from that. I do get a soft code B2161 historic code (brake lamp output open) occasionally, but that's because of the triple play module converting the rear signals to R/B/T. Supposedly it stops throwing this code if you have them flash the BCM to enable rear turn signals to operate as stop lamps, according to a few people on the net.
EDIT:
Side note, looking for something else, came across a Harley service bulletin that for 2014-later bikes,when swapping to LED turns, the procedure is to turn on the hazards and let them flash 12 times. Apparently the BCM ignores the first two flashes and over the next 10, it learns the new load and should be good to go. So may not even take a full 2-4 minutes of flashing.
And in re-reading my post, I don't know if there's a difference between BCM and canBus, when the change over occurred, or if the procedure is different. I know what a BCM is, that it's a module (body control module), but I have no idea what a canbus is. I'm still learning all the modern stuff.