Thanks for those newTIS links!
Drilling down to the i3, there are a LOT of subheadings that seem to make no sense whatsoever. "28 Twin-clutch gearbox (DKG)"?
I think my problem is with the plug locking mechanism, but I decided to take it to the dealer before tackling bumper removal.
A note from the dealer drop-off...
They have seen this issue before and suggested that, not only could the locking plunger be at fault, failures of the control module and/or the interconnect between the two have been observed.
Once I get the i3 back I'll update this thread.