Connect GDS to Data Link Connector(DLC).
Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.
If DTC status is current condition, go to following procedure. And, if it is histroy DTC, erase it and check that MIL is ON again.
Erase DTC C1646.
Recheck EPB whether C1646 is still active. If so, check TCU related item.