When I trained on the Bizhub 423 series I remember L codes and such. The other tech I work with went to school on the Bizhub 751 and such and he doesn't remember anything like that from class. I didn't see anything in the service manual or theory of operation and we don't really have any machines pushing that far yet. I was curious though if the 751's have a similar function on them that tosses out a code when a parts life counter is met.