Hello, I do not believe this machine gives you a TCU level reading, I do know it will give you an event log message that the TCU almost full, and replace TCU message. The TCU is designed to last 36,000 prints, so based on that I would see where the page count is at and go from there. Here is the part number if you do not have it.
CC493-67913-Toner collection unit
Event log error message:
10.31.60-Toner collection unit almost full
10.31.70-Replace Toner Collection Unit
Hope this helps.....