Brother HL-3170CDW - Manual (Page 138)

Routine Maintenance
132
4
g
Close the top cover of the machine.
When you replace the belt unit with a new one, you must reset the belt unit counter by completing the
following steps:
a
Press a while holding down Go on the machine's control panel.
b Press a or b to display Belt Unit. Press OK.
c Press a for Reset to reset the belt unit counter.