Evening chap - I'm having a similar issue, fitted harnesses and removed factory seatbelts and getting the front pretensioner airbag light on. RSTuner software shows the circuit is open and when i plug the belts back in to the harness, the fault is cleared...
Did you managed to resolve this and if so, how?
I have the RSTuner with ABS module enabled but it doesn't have the seatbelt centre pretensioner listed so I can't disable via software