DT556: UndershootDT556 reported undershoot on 13.04. Observed brake blending on LDC log. Fault time(s): 1) 20:55:45, 2)19:40:34, 3)17:40:16, 4) 16:45:23 ~~~~~ Check all car brake pressure - ok Replaced 3556 ACU & BCU for preventive measure. Carryout function check - ok . Depot shunting - ok  /KUMAR/14.04.22