They are the same machine but each company that puts their name on it wants the exclusive toner/IU rights. So chips are different as well as the end...
the low toner condition is triggered by a reed switch on the side of the toner hopper. these can be a bit flaky. you may need to remove, disassemble...
replace the drum and dev (again), fire it up with the side door open, get into service mode>counters, reset the drum and dev count, then exit out of...