In Australia HDI these active exhaust units are lying around in every Harley workshop and home garage if an HD lives or has ever lived there since 2007.
We "piss them off" always as part of any stage 1 or exhaust change. I have several myself, brand new and would make good paperweights.
Our USA based cousins would have no clue what they are ! They are part of the "Euro" noise reduction rules.
I always toggle them to "off" when doing the first then any subsequent ECM flashing. Then I use "US Domestic" calibrations to final road tune the bikes.
Some folks leave them attached to avoid the fault code you describe, but manually screw/epoxy resin/jam them permanently open physically.
I am mindful that there is no "MOT" annual roadworthy test in Western Australia , and perhaps you have to keep them active for that reason?
All of the HDI models sold here run WAY better with them "toggled off" and/or physically kept open.
That setting the bikes are always running thru both mufflers not a part time 2 into 1 where onlt one muffler is used prt of the time.