TC encountered fault at front DT car. Train routed back to depot ~~~~~ #3675 fault code 308, 314, 330, 331. Having stuck brake while train entering maint pit. Further check confirmed ACU solenoid port heavy air leak while put to coast. Replaced ACU and brake cycle test-ok. ACU-New s/n: 1511-042  ,,Old s/n: 1540-073. Not: 2130532 raised. #ACU fleetwide c/o done also. Done by Jack/Sateesh/Koh. 13/02/20.